BASED GEOPOLYMER CONCRETE A dissertation …libres.uncg.edu/ir/uncc/f/Sanusi_uncc_0694D_10405.pdf · 8.1.2 Description of the PHREEPLOT Input File 119 8.2 Procedure for the PHREEPLOT

MOBILIZATION OF OXYANION FORMING TRACE ELEMENTS FROM FLY ASH

BASED GEOPOLYMER CONCRETE

by

Olanrewaju Abdur-Rahman Sanusi

A dissertation submitted to the faculty of

The University of North Carolina at Charlotte

in partial fulfillment of the requirements

for the degree of Doctor of Philosophy in

Infrastructure and Environmental Systems

Charlotte

2012

Approved by:

_____________________________

Dr. Vincent Ogunro

_____________________________

Dr. John Daniels

_____________________________

Dr. Brett Tempest

_____________________________

Dr. Miguel Pando

_____________________________

Dr. Ertunga Ozelkan

_____________________________

Dr. Carlos Orozco

ii

©2012

Olanrewaju Abdur-Rahman Sanusi

ALL RIGHTS RESERVED

iii

ABSTRACT

OLANREWAJU ABDUR-RAHMAN SANUSI. Mobilization of oxyanion forming trace

elements from fly ash based geopolymer concrete (Under the direction of Dr. VINCENT

OGUNRO)

The suitability of fly ash based geopolymer concrete as a replacement for ordinary

Portland cement (OPC) concrete depends on the mobility of elements from the material. Due

to the alkaline nature of geopolymer concrete, there is a potential for the release of oxyanion

forming elements such as As, Cr and Se which are characterized by their high mobility in the

alkaline environment. In this study, geopolymer concretes were produced with varying

amount of hydrated lime and subjected to tests that include pH dependence test, Dutch

availability test, tank test, water leach test, mineralogical, microstructural analysis and

geochemical modeling using PHREEQC/PHREEPLOT. The results of this study confirmed

that As and Se and other oxyanion forming elements exhibit higher mobility in the alkaline

pH. Further investigation using the Dutch availability and tank test showed that As have the

highest mobility from all the geopolymer concretes. It also reveals that the mobility of As and

Se reduces with time as the element becomes depleted in the matrix. Mobility of the two

elements was observed to be lowest in the geopolymer concrete with 1% hydrated lime which

suggest that the addition of 1% hydrated lime lead to reduction in the mobility of As and Se.

Cr on the other hand have the same low mobility from all the geopolymer, this suggest that

hydrated lime addition has no effect on the mobility the element. Finally,

PHREEQC/PHREEPLOT identifies species of leached elements as As (5), Se (6) and Cr (6).

These species of As and Se have low toxicity whereas the species of Cr is of the more toxic

form, but it is released in level far below the Maximum Concentration Level (MCL) set by

EPA for drinking water.

iv

DEDICATION

This dissertation is dedicated to my parents, siblings and friends.

v

ACKNOWLEDGMENTS

My sincere gratitude goes to my advisor, Dr. Vincent Ogunro for his guidance,

valuable suggestions and encouragement throughout my doctoral studies. I would like to

extend my appreciation to members of my committee – Drs. Brett Tempest, John Daniels,

Miguel Pando, Ertunga Ozelkan and Carlos Orozco – for their time, support and

constructive comments.

A big thank you to Marge Galvin-Karr of Duke Energy laboratory for her

assistance in analyzing all leachates from my leaching tests. Many thanks to Claire

Chadwick for giving me the freedom to impose on her for assistance with analysis of

samples and use of instruments at the department of Geography and Earth Sciences.

Special thanks to Mike Moss for his help in various ways in the workshop. I would also

like to thank Alec Martin for teaching me how to use the XRD and SEM. Sincere

appreciation to Elizabeth Scott and Erin Morant for their assistance with various

administrative tasks related to my study.

My deepest appreciation is due to my parents, siblings (Diran, Titi, Tope, Tayo,

Iyabo, Latifah and Gary), lab buddies (Yogesh and Ari), friends (Onyewuchi, Femi,

Appolo, Ayoola, Amanda, Toyin) and others too numerous to mention. Thank you all for

having confidence and believing in me. Finally, I acknowledge the support of the

department of civil and environmental engineering and the graduate school for awarding

me the graduate assistant support plan (GASP) fellowship.

vi

TABLE OF CONTENTS

LIST OF FIGURES xi

LIST OF TABLES xv

LIST OF ABBREVIATIONS xvii

CHAPTER 1: INTRODUCTION 1

1.1 Background 1

1.2 Problem Description 5

1.3 Significance and Benefit of the Study 6

1.4 Research Goal and Objectives 6

1.5 Research Hypotheses 7

1.6 Scope of Work 8

1.7 Organization of the Dissertation 8

CHAPTER 2: LITERATURE REVIEW 10

2.1 Historical Development of Geopolymer as Alternative Binder 10

2.2 Basic Concept of Geopolymer 11

2.2.1 Source Materials for Geopolymer Synthesis 12

2.2.2 Chemistry and Reaction Mechanisms 15

2.2.3 Structure of Geopolymer 17

2.4 Characteristics and Application of Geopolymer 19

2.5 Background on Leaching and Mobility of Elements 20

2.5.1 Mobility of Elements from Geopolymer 21

2.6 Oxyanion Forming Trace Elements 25

2.6.1 Occurrence and Chemistry of Arsenic, Chromium and Selenium 26

2.6.2 Environmental Aspect and Toxicity of As, Cr and Se 27

vii

2.7 Methods of Immobilizing the Leaching of Oxyanion Elements 28

2.7.1 Incorporation into Ettringite Structure 29

2.7.2 Incorporation into Hydrocalumite Structure 30

2.7.3 Incorporation into Monosulfoaluminate Structure 31

2.7.4 Incorporation into Calcium Silicate Hydrate (CSH) 31

2.7.5 Formation of Precipitates 32

2.8 Mineralogical and Microstructural Characterization of Geopolymer 32

2.9 Geochemical Modeling 33

2.10 Summary 35

CHAPTER 3: EXPERIMENTAL PROTOCOL 37

3.1 Research Approach 37

3.2 Materials 37

3.2.1 Coal Fly Ash (CFA) 37

3.2.2 Silica Fume (SF) 37

3.2.3 Sodium Hydroxide (NaOH) 38

3.2.4 Hydrated lime (Ca(OH)2) 38

3.2.5 Aggregates 38

3.3 Experimental Method 38

3.4 Quality Assurance and Quality Control 40

3.5 Statistical Analysis of Data 41

3.6 Pilot Study 41

3.6.1 Element Mobility from Fly Ash Based Geopolymer Paste 41

3.6.2 Leaching of Oxyanion Forming Elements from Fly Ash Based 45

Geopolymer Paste

3.6.3 Mitigating Leachability from Geopolymer Concrete using RCA 47

viii

3.6.4 Influence of Lime on Strength and mobility of Elements from 49

Geopolymer Paste

CHAPTER 4: SYNTHESIS OF GEOPOLYMER CONCRETE AND SAMPLE 52

PREPARATION

4.1 Synthesis and Preparation of the Geopolymer Concretes 52

4.2 Sampling and Sample Preparation 53

4.3 Summary 56

CHAPTER 5: CHARACTERIZATION OF THE MATERIALS 58

5.1 Chemical Composition of X-Ray Fluorescence (XRF) Analysis 58

5.2 Particle Size Distribution (PSD) 59

5.3 Compressive Strength of the Geopolymer Concrete 62

5.4 Acid and Base Neutralization Capacity (ANC/BNC) 65

5.5 Material Natural pH 68

5.6 Moisture Content and Bulk Density 69

5.7 Summary 69

CHAPTER 6: LABORATORY LEACHING TEST METHODS 71

6.1 Introduction 71

6.2 pH Dependence Leaching test 72

6.3 Dutch Availability Test 80

6.4 Tank Test 83

6.4.1 Leachability Index (LX) of the Elements 89

6.4.2 Depletion of the Elements in Relation to Availability 91

6.5 Water Leach Test 94

6.6 Risk Associated with Release of the Oxyanion Elements 97

6.7 Summary 99

ix

CHAPTER 7: MINERALOGICAL AND MICROSTRUCTURAL 101

CHARACTERIZATION

7.1 Mineralogical and Microstructural Analysis 101

7.2 X-Ray Diffraction (XRD) Analysis 101

7.3 Scanning Electron Microscope (SEM) Analysis 108

7.4 Energy Dispersive X-Ray Spectroscopy (EDX) Analysis 112

7.5 Summary 116

CHAPTER 8: SPECIATION MODELING USING PHREEQC/PHREEPLOT 117

8.1 Background on PHREEQC/PHREEPLOT 117

8.1.1 The PHREEPLOT Database 118

8.1.2 Description of the PHREEPLOT Input File 119

8.2 Procedure for the PHREEPLOT Speciation Modeling 121

8.3 Model Simulation Results and Interpretation 123

8.4 Validation of the Model Output 126

8.5 Summary 127

CHAPTER 9: CONCLUSIONS AND RECOMMENDATIONS 128

9.1 Conclusions 128

9.1.1 Synthesis of Geopolymer Concrete 128

9.1.2 Leaching of Elements from Geopolymer Concrete 130

9.1.3 XRD and SEM/EDX Analysis of the Geopolymer Concretes 133

9.1.4 Distributions of Species of As, Cr and Se 134

9.1.5 Overall Conclusions 134

9.2 Limitations of the Study 136

9.3 Recommendations for Future Work 137

x

REFERENCES 138

APPENDIX A: MIX DESIGN FOR THE GEOPOLYMER CONCRETE 150

APPENDIX B: COMPRESSIVE STRENGTH MEASUREMENTS FOR THE 151

GEOPOLYMER CONCRETE MIXES

APPENDIX C: STATISTICAL ANALYSIS OF THE GEOPOLYMER 152

CONCRETE COMPRESSIVE STRENGTH

APPENDIX D: PH DEPENDENCE LEACHING TEST RESULTS FOR 160

OTHER ELEMENTS

APPENDIX E: ENLARGED CUMULATIVE PLOT OF THE ELEMENTS 165

APPENDIX F: INPUT FILE FOR PHREEQC/PHREEPLOT 167

APPENDIX G: OUTPUT FILE FOR PHREEQC/PHREEPLOT 170

APPENDIX H: MOLAL CONCENTRATION OF ELEMENTS OBTAINED 181

FROM THE MODEL

xi

LIST OF FIGURES

FIGURE 2-1: Simplified representation of geopolymer reaction mechanism. 17

FIGURE 2-2: Polymeric precursor that form geopolymers 18

FIGURE 2-3: Conceptual structure of Na-PSS geopolymer 19

FIGURE 2-4: Schematics of ettringite crystal structure 29

FIGURE 2-5: Oxyanion substituted ettringite structure 30

FIGURE 2-6: Schematics of hydrocalumite structure 30

FIGURE 2-7: Schematics of monosulfoaluminate structure 31

FIGURE 3-1: Mobility of elements from the geopolymer paste (category 1) 43




FIGURE 3-5: Compressive strength of the fly ash based geopolymer concretes 48

FIGURE 3-6: Concentration of the leached oxyanion forming elements 48

FIGURE 4-1: Schematics of the geopolymer concrete production 54

FIGURE 4-2: Steel pestle and mortar used in crushing the geopolymer concrete 54

FIGURE 4-3: Cone and quartering process 55

FIGURE 4-4: Crushed and size reduced geopolymer concrete sample 55

FIGURE 4-5: Rocklab ring grinder used in grinding the geopolymer concrete samples 56

FIGURE 4-6: Cured geopolymer concrete a) cured without heat, b) heat cured 57

FIGURE 5-1: Particle size distribution of the aggregates 59

FIGURE 5-2: Laser diffraction particle size analyzer 60

FIGURE 5-3: Particle size distribution of CFA and SF (volume % ) 61

xii

FIGURE 5-4: Particle size distribution of CFA and SF (cumulative volume %) 61

FIGURE 5-5: Compressive strength of the geopolymer concrete cured with heat 62

FIGURE 5-6: Compressive strength of geopolymer concrete cured without heat 64

FIGURE 5-7: ANC/BNC curve of CFA 65

FIGURE 5-8: ANC/BNC curve of SF 66

FIGURE 5-9: ANC/BNC curve of GPC 66

FIGURE 5-10: ANC/BNC curve of GP1 67



FIGURE 6-1: pH dependence test experimental setup 73

FIGURE 6-2: pH dependence mobility of As from the CFA and SF 74

FIGURE 6-3: pH dependence mobility of Cr leached from the CFA and SF 75

FIGURE 6-4: pH dependence mobility of Se from the CFA and SF 76

FIGURE 6-5: pH dependence mobility of As from the geopolymer concretes 77

FIGURE 6-6: pH dependence mobility of Cr from the geopolymer concretes 78

FIGURE 6-7: pH dependence mobility of Se from the geopolymer concretes 79

FIGURE 6-8: Schematics of the Dutch availability test 81

FIGURE 6-9: Availability of As, Se and Cr from the starting materials 81

FIGURE 6-10: Availability of As, Cr and Se from geopolymer concrete samples 82

FIGURE 6-11: Schematic of the tank leaching test 84

FIGURE 6-12: the tank leaching test setup 84

FIGURE 6-13: Release of As from the geopolymer concrete samples 85

FIGURE 6-14: Release of Se from the geopolymer concrete samples 87

xiii

FIGURE 6-15: Release of Cr from the geopolymer concrete samples 88

FIGURE 6-16: As availability in tank test in relation to total availability 92

FIGURE 6-17: Se availability in tank test in relation to total availability 92

FIGURE 6-18: Cr availability in tank test in relation to total availability 93

FIGURE 7-1: Schematic of the XRD setup 102

FIGURE 7-2: XRD diffractogram for the CFA and SF used 103

FIGURE 7-3: XRD diffractogram for the GPC geopolymer concrete 104

FIGURE 7-4: XRD diffractogram for the GP1 geopolymer concrete 105



FIGURE 7-7: JOEL SEM equipped with energy dispersive spectrometry (EDX) 108

FIGURE 7-8: SEM micrograph of CFA and SF 109

FIGURE 7-9: SEM micrograph of the GPC geopolymer concrete 110

FIGURE 7-10: SEM micrograph of the GP1 geopolymer concrete 110



FIGURE 7-13: EDX spectrum of CFA 113

FIGURE 7-14: EDX spectrum of SF 113

FIGURE 7-15: EDX spectrum of GPC 113

FIGURE 7-16: EDX spectrum of GP1 114



FIGURE 8-1: Typical distribution of As species from the PHREEPLOT simulation 124

xiv

FIGURE 8-2: Typical distribution of Se species from the PHREEPLOT simulation 125

FIGURE 8-3: Typical distribution of Cr species from the PHREEPLOT simulation 126

FIGURE D-1: pH dependence mobility of elements from CFA and SF 160

FIGURE D-2: pH dependence mobility of elements from CFA and SF 161

FIGURE D-3: pH dependence mobility of Mo and V from the CFA and SF 162

FIGURE D-4: pH dependence mobility of Mo and V from the geopolymer concretes 162

FIGURE D-5: pH dependence mobility of elements from the geopolymer concretes 163

FIGURE D-6: pH dependence mobility of elements from the geopolymer concretes 164

FIGURE E-1: Plot showing enlarged cumulative release of As 165

FIGURE E-2: Plot showing enlarged cumulative release of Se 165

FIGURE E-3: Plot showing enlarged cumulative release of Cr 166

xv

LIST OF TABLES

TABLE 2-1: Chemical requirement for fly ash classification (% mass) 14

TABLE 2-2: Typical chemical composition of coal fly ash and cement (%) 14

TABLE 2-3: Typical total amount of some trace elements present in CFA 15

TABLE 2-4: Summary of various leaching test methods 22

TABLE 2-5: Chemical properties and MCL of As, Cr and Se 27

TABLE 2-6: Redox states of the oxyanions in alkaline environment 28

TABLE 3-1: Experimental phases for the dissertation 39

TABLE 3-2: Experimental conditions for the availability tests 46

TABLE 4-1: Mix design for the geopolymer concrete (kg/m3) 53

TABLE 5-1: Chemical composition of the CFA and SF (mass %) 58

TABLE 5-2: Natural pH of the materials 68

TABLE 5-3: Moisture content and bulk density of the materials 69

TABLE 6-1: Relevant leaching test during life cycle of cementitious materials 72

TABLE 6-2: Leachability index (LX) of As, Se and Cr from geopolymer concrete 90

TABLE 6-3 :The LX range for different rate of mobility 91

TABLE 6-4: Percentage depletion in relation to total available fraction 94

TABLE 6-5: Temp and pH of the water leach test leachates 94

TABLE 6-6: concentration of cations in the water leach test leachates 95

TABLE 6-7: Concentration of anions in the water leach test leachate 96

TABLE 6-8: TCLP Regulatory limits of As, Cr and Se 97

TABLE 6-9: Comparison of amount leached from geopolymer (mg/kg) 98

TABLE 6-10: Residential risk based screening levels 99

xvi

TABLE 7-1: Mineral phases detected in the geopolymer concretes 107

TABLE 7-2: Elemental composition of the geopolymer concretes 115

TABLE 8-1: Databases associated with PHREEPLOT 118

TABLE 8-2: Mineral phases manually added to the simulation 122

TABLE 8-3: Comparison of input and PHREEPLOT model output concentration 127

TABLE A-1: Mix design for the geopolymer concrete (kg/m3) 150

TABLE A-2: Percentage of each component in the geopolymer concrete (%) 150

TABLE A-3: Explanation of notations used in mix design 150

TABLE B-1: Compressive strength of the geopolymer concrete (psi) 151

TABLE B-2: Compressive strength of geopolymer concrete (MPa) 151

TABLE H-1: Molal concentration from simulation at pH 11.588 181

xvii

LIST OF ABBREVIATIONS

AMSCD American mineralogist crystal structure database

ANC acid neutralization capacity

As arsenic

ASTM American society for testing and materials

BNC base neutralization capacity

CA coarse aggregate

CASH calcium aluminosilicate hydrate

Cd cadmium

CFA coal fly ash

Cr chromium

Cs cesium

CSH calcium silicate hydrate

Cu copper

De effective diffusion coefficient

DI deionized water

DL detection limit

EDX energy dispersive x-ray spectroscopy

ELT equilibrium leach test

EP Tox extraction procedure toxicity test

FA fine aggregate

Fe iron

Gt gigaton

xviii

Hg mercury

IC ion chromatography

ICP-AES inductively coupled plasma atomic emission spectrometer

ICP-MS inductively coupled plasma mass spectrometer

L/S liquid to solid ratio

LOI loss on ignition

LX leachability index

MCL maximum contaminant level

MEP multiple extraction procedure

Mo molybdenum

MPa megapascal

Mt megaton

NEN Netherlands standardization institute

OPC ordinary Portland cement

Pb lead

ppm part per million

PS polysialate

PSD particle size distribution

PSDS polysialate disiloxo

PSS polysialate siloxo

RCA recycled concrete aggregate

Sb antimony

SCM supplementary cementitious materials

xix

Se selenium

SEM scanning electron microscope

SF silica fume

SI saturation index

SPLP synthesis precipitation leach procedure

TCLP toxicity characteristics leaching procedure

USEPA united states environmental protection agency

V vanadium

W tungsten

WLT water leach test

XRD x-ray diffraction

XRF x-ray fluorescence

Zn zinc

CHAPTER 1: INTRODUCTION

This chapter presents the main research problem addressed in this PhD

dissertation together with the main research objectives and hypotheses. The chapter starts

with a brief background section related to concrete and geopolymer concrete to provide

the reader with the right context used to formulate the problem statement and associated

objectives, hypotheses and work plan.

1.1 Background

Concrete is the most widely used material in the world after water (van Oss and

Padovani, 2002; Hardjito and Rangan, 2005; Damtoft et al., 2008), and a very important

construction material used in many civil engineering applications such as buildings,

sidewalks, bridges, dams and industrial plants. The material is typically manufactured

from components that include approximately 65% to 80% aggregates (fine and coarse),

between 10% to 12% cement, a maximum of 21% water and between 0.5% to 8% air

content (van Oss and Padovani, 2003; Quiroga and Fowler, 2004). All these components

are in percentage by weight of the total. Cement is the major component of concrete

because it is the binding agent holding the aggregates together thereby giving the

conglomerate its characteristic strength and durability. Fine aggregates utilized in

concrete are typically natural sand or fine crushed stones with particle size that range

from 150 µm to a maximum of 4.75 mm while coarse aggregates are typically natural

2

gravel or granitic stones with a minimum particle size of 4.75 mm (Badur and

Chaudhary, 2008).

Aggregates are a very important component of the concrete mix that has a great

effect on the resulting concrete physical properties. In order to obtain concrete of specific

characteristics, other components such as superplasticizers and retarders can be added

during the mixing process to respectively improve the workability and reduce the setting

time of the concrete (Badur and Chaudhary, 2008). Ordinary Portland Cement (OPC) is

the most commonly used type of cement; it sets and hardens in the presence of water due

to hydration reaction. In making construction grade concrete, cement usage can typically

be either 100% OPC or a mixture of OPC and other supplementary cementitious

materials (SCM) such as steel slag and fly ash (Struble and Godfrey, 2004).

Manufacturing of OPC involves mining limestone and shale, heating the mixture

(limestone and shale) in a rotary kiln to convert the limestone into lime via a process

known as calcination, and finally grinding the resulting cement clinker with gypsum

(Struble and Godfrey, 2004). This production process is very energy intensive and

involves the release of greenhouse gases such as CO2 and N2O into the atmosphere. For

every metric ton of cement produced, there is approximately 0.8 metric ton CO2 released

to the atmosphere (Gartner, 2004). An estimated 80.2 megatons (Mt) CO2 per year were

generated from cement production in the United States between 1996-2000 (van Oss and

Padovani, 2002). Apart from the emission of CO2, other environmental issues associated

with cement production are dust, noise, and vibration.

One way of reducing CO2 emission associated with concrete usage is to reduce

the amount of cement utilized in making concrete by increasing the use of SCM

3

(Bremner, 2001). There have been up to 35% replacement of OPC in concrete with SCM

such as fly ash (Tempest, 2010), which is a pozzolan that reacts with Ca(OH)2 from OPC

hydration to form additional calcium silicate hydrate (CSH) gel thereby improving the

later day strength of concrete (Hardjito and Rangan, 2005). Most of the fly ash used as

SCM in concrete comes from coal fired power plants. According to the American Coal

Ash Association, about 72 million tons of coal fly ash is produced in the United States

annually, with only 44% being re-utilized in various applications and the remaining

disposed in landfills (ACAA, 2008). This huge abundance of fly ash created an

opportunity for achieving high replacement of OPC in concrete with the material.

Coal fly ash (CFA) is a highly heterogeneous material that is enriched with major

elements such as silicon (Si), aluminum (Al), calcium (Ca) and iron (Fe) accounting for

nearly 90% of the fly ash composition (Jankowski et al., 2006; Jegadeesan et al., 2008;

Izquierdo and Querol, 2011). Other elements present in CFA include trace elements such

as antimony (Sb), arsenic (As), boron (B), cadmium (Cd) chromium (Cr), cobalt (Co),

lead (Pb), selenium (Se), nickel (Ni), zinc (Zn) and copper (Cu) which account for a

small percentage of the bulk composition (Dogan and Kobya, 2006; Izquierdo and

Querol, 2011). The composition of elements present in CFA varies greatly mainly due to

the coal source, particle size of the coal, combustion process and type of ash collector

(Jankowski et al., 2006; Jegadeesan et al., 2008). The presence of the high content of Si,

Al and Ca makes coal fly ash a suitable SCM and source aluminosilicate material for

synthesis of alkali activated binder. But the presence of trace elements that are

susceptible to leaching from the material into the environment may impact the suitability

of coal fly ash for beneficial reuse (Jegadeesan et al., 2008).

4

In the 1970s, Prof Davidovits pioneered the development of a new binder termed

―geopolymer‖ (Davidovits, 1991) which can completely replace Portland cement in

concrete. This new binder is an inorganic three-dimensional (3D) polymeric material

made from the reaction of any material rich in silica and alumina (aluminosilicate) with a

strong alkaline solution (activator) that contains sodium silicate and or sodium hydroxide

(Duxson et al., 2007; Komnitsas and Zaharaki, 2007; Provis and van Deventer, 2009).

Aluminosilicate materials such as metakaolin, kaolinite, steel slag, coal fly ash and rice

husk ash also have been successfully used in the production of geopolymer (Nazari et al.,

2011).

Studies have shown that geopolymer possesses excellent properties that include

high compressive strength, acid and heat resistance, low shrinkage and the potential or

ability to immobilize hazardous contaminants within its matrix (Davidovits, 1991;

Komnitsas and Zaharaki, 2007; Tempest, 2010), making it a suitable replacement for

cement in concrete and waste stabilization. In the past years, there has been rapid

progress in the development of geopolymer from coal fly ash, research groups from

Curtin University of Technology and the University of Melbourne in Australia which are

leading in this area of research. Hardjito and Rangan (2005) from Curtin University of

Technology pioneered the production of concrete specimens using fly ash based

geopolymer as binder instead of OPC. In 2008, our materials research team at the

University of North Carolina at Charlotte led by Dr. Brett Tempest with support of Drs.

Janos Gergely and Vincent Ogunro started work on fly ash based geopolymer concrete.

The majority of the work to date completed focused on engineering characterization of

5

geopolymer concrete for structural components like columns, reinforced beams, and large

scale girders (Tempest, 2010).

Most of the research that has been done on geopolymer paste, mortar and concrete

to date has been extensively on understanding their chemistry and reaction mechanism,

curing conditions, durability, mineralogy, microstructure and other engineering

properties. In contrast, there has been very little environmental related characterization

such as the leaching of potentially hazardous elements.

1.2 Problem Description

The limited environmental characterization conducted on geopolymer have shown

that potentially toxic elements can leach out when the material is exposed to aqueous

environment (Bankowski et al., 2004; Xu et al., 2006; Izquierdo et al., 2009), which

might be harmful to human and the environment when released in high concentrations.

The majority of these environmental characterization have focused primarily on cationic

elements (Xu et al., 2006; Izquierdo et al., 2009) such as lead (Pb), copper (Cu), mercury

(Hg), cesium (Cs), zinc (Zn), cadmium (Cd) and iron (Fe), and very limited study on

elements that form oxyanionic species (Bankowski et al., 2004; Izquierdo et al., 2010)

such as arsenic (As), selenium (Se), chromium (Cr), vanadium (V), antimony (Sb),

molybdenum (Mo), and tungsten (W) which are characterized by their high mobility at

neutral to alkaline pH.

Due to the alkaline nature of geopolymer, and the known high mobility of

oxyanion forming elements (As, Cr, Se) at high pH, their potential release from

geopolymer make them elements of great environmental concern. In order to demonstrate

the suitability of fly ash based geopolymer concrete as an everyday construction material,

6

there is a need to minimize the mobility of these elements during the service life and at

end of life of a geopolymer concrete product.

1.3 Significance and Benefit of the Study

Oxyanion forming trace elements (e.g As, Cr, Se) are toxic at very low

concentration thereby making their potential immobilization or decreased mobility

through addition of lime an important factor in the determination of geopolymer as a safe

alternative to cement in construction and waste stabilization. The success of this research

would add to the knowledge of reducing any concern regarding potential environmental

impact of geopolymer which has not been sufficiently investigated by many researchers,

and would produce important parameters for life cycle analysis that could important in

selecting the most environmentally responsible manner of utilizing the product.

1.4 Research Goal and Objectives

The overall goal of the research is to assess/characterize the leaching mechanisms

of oxyanion forming trace elements from coal fly ash based geopolymer concrete/mortar

and investigate the effect of additives such as lime on reduction of element mobility from

the geopolymer concrete by rendering the element partially insoluble. The specific

objectives of the research are:

1. To determine the release of oxyanion elements (As, Cr, Se) from fly ash based

geopolymer concrete under service life (monolithic) and end of service life

(granular) conditions using appropriate tests.

2. To assess the potential to decrease mobility, or even total immobilization of

oxyanion elements (As, Cr, Se) in geopolymer concrete by means of using

hydrated lime as an admixture.

7

3. To determine the maximum amount of oxyanion forming elements that would be

released under the worst case scenario when the material is pulverized.

4. To determine if there is formation of calcium containing mineral phases, calcium

precipitates or calcium metalates in the produced geopolymer concrete.

5. To identify probable mechanisms responsible for immobilization of the oxyanion

forming elements (if there is any immobilization).

6. To determine the species of the oxyanion elements (As, Cr, Se) released from fly

ash based geopolymer concrete and their potential environmental impacts.

1.5 Research Hypotheses

In conducting this study, the following hypotheses were formulated to address the

goal and specific objectives of the research:

1. Oxyanion elements (As, Cr, Se) are present in leachates from fly ash based

geopolymer concrete.

2. Oxyanion forming trace elements exhibit different leaching behavior than other

elements that are leached from the alkaline fly ash based geopolymer.

3. Standard leaching test methods conducted at a neutral pH are adequate for

predicting the leaching of oxyanion forming elements.

4. Calcium containing mineral phases such as ettringite, hydrocalumite,

monosulfoaluminate, calcium metalates and calcium silicate hydrates (CSH) are

effective for immobilizing oxyanion forming elements via ion substitution.

5. Leaching of these oxyanion forming elements can be mitigated by the addition of

extra calcium in the form of lime during the geopolymer synthesis, which would

lead to the formation of oxyanion substituted calcium containing mineral phases

8

in addition to the geopolymer phase without affecting the durability of the

geopolymer.

1.6 Scope of Work

This dissertation focuses mainly on geopolymer concrete produced from class F

fly ash (low calcium), silica fume (as the additional silica source), hydrated lime

(Ca(OH)2) as source of additional calcium and aggregates that make up not more than

70% of the concrete mix that has a target 28 days compressive strength of 41 MPa (6000

psi). The study was based solely on laboratory investigation that focuses on the service

life condition (monolith state) and end of life condition (granular state) of the

geopolymer. Laboratory speciation analysis was not performed to determine the species

of the elements leached from the geopolymer concrete. Geochemical modeling using

PHREEQC/PHREEPLOT was employed in predicting the species of the elements in the

leachates.

1.7 Organization of the Dissertation

The dissertation is organized into nine chapters. Chapter 1 describes the impetus

for the study of the mobility of oxyanion forming trace elements from fly ash based

geopolymer concrete. Chapter 2 presents review of relevant literature on geopolymer and

leaching of elements. Topics covered in this chapter include the historical development of

geopolymer as an alternative binder, source material used for geopolymer synthesis, and

mobility/immobilization of the oxyanion forming trace elements.

Chapter 3 describes the research approach used, the starting materials, summary

of the experimental methods, preliminary investigation completed, procedures for quality

assurance and quality control, and statistical tools employed for data analysis.

9

Geopolymer concrete synthesis is presented in Chapter 4. The chapter also describes

sample preparation methods used in the study. Chapter 5 focuses on materials

characterization such as particle size distribution (PSD), X-Ray fluorescence (XRF)

analysis, and acid/base neutralization capacity (ANC/BNC). The entire laboratory

leaching test methods employed and results obtained are presented in Chapter 6.

Chapter 7 contains the mineralogical and microstructural characterization of the

starting materials and produced geopolymer concrete samples using X-Ray diffraction

(XRD) and scanning electron microscope (SEM)/energy dispersive spectroscopy (EDX)

analysis. Chapter 8 describes the application of PHREEQC/PHREEPLOT to predict the

speciation of oxyanion elements from the geopolymer concrete leachates. The last

chapter of the dissertation, Chapter 9 presents the conclusions drawn from this

investigation and presents recommendations for future research work.

CHAPTER 2: LITERATURE REVIEW

2.1 Historical Development of Geopolymer as Alternative Binder

Portland cement has been the dominant binder used in concrete and mortar since

it was developed by Joseph Aspdin in the early 19th century. It is the most abundant

building material due to its versatility and economic values, with annual worldwide

production estimated to be around 3 gigatons (Gt) (Juenger et al., 2010). However, there

are environmental issues such as huge energy consumption, particulate emission and

enormous release of CO2 arising from the manufacturing of this binder. Infact, it is

considered one of the largest industrial emitter of CO2, a greenhouse gas that causes

global warming (van Oss and Padovani, 2002). With the growing concern about threats

posed by increased release of CO2 to the atmosphere, attempts have been made at

reducing the percentage of cement used in making concrete by replacing them with SCM

such as coal fly ash, ground blast furnace slag and silica fume in the hope of reducing the

overall environmental impact (Juenger et al., 2010). Researchers also seek to find

alternative binders with reduced energy use and low CO2 emission that can completely

replace cement which led to the development of alkali activated binders.

Alkali activated binders were considered as an alternative binder due to their

durability, low energy and reduced CO2 emission, hence resulting in reduced

environmental impacts. These binders are sometimes referred to as inorganic polymer,

geopolymer, alkali activated cement, geocement and soil silicate, with geopolymer being

11

the most commonly used name (Duxson et al., 2007; Komnitsas and Zaharaki, 2007;

Juenger et al., 2010). They are produced from the reaction of aluminosilicate raw

materials with an alkaline solution.

Although the term geopolymer was coined by Joseph Davidovits in the 1970s to

describe an alkali activated binder developed from metakaolin with the hope of producing

a fire resistant plastic material (Davidovits, 1991), similar alkali activated binders have

been described earlier by Purdon in the 1940s and Glukhovsky in the 1950s (Roy, 1999;

Komnitsas and Zaharaki, 2007; Škvára, 2007; Pacheco-Torgal et al., 2008b). The

aluminosilicate source material used by most of the earlier researchers was ground blast

furnace slag. It was reported that activation of blast furnace slag led to an alkali activated

systems that contains both calcium silicate hydrate gel (CSH) and aluminosilicate phase

since the blast furnace slag is rich in calcium (Komnitsas and Zaharaki, 2007), while the

activation of metakaolin produced only a zeolite-like aluminosilicate phase (Sakulich,

2009).

2.2 Basic Concept of Geopolymer

As discussed in the previous section, geopolymer is a generic name used to

describe all alkali activated binders synthesized from the reaction of an aluminosilicate

source with a strong alkali activating solution that contains a mixture of Na2SiO3 and

NaOH or KOH solution (Pacheco-Torgal et al., 2008a). The aluminosilicate material is

dissolved by the alkali solution which also provides additional silicate required for the

geopolymerization process. Silica fume is sometimes used instead of Na2SiO3 as the

source of additional reactive silica (Tempest, 2010). Geopolymer gel formation is

achieved by the application of mild heat at a temperature less than 100oC.

12

Many curing regime have been implemented for geopolymer, Kong and Sanjayan

(2010) cured geopolymer specimens at ambient temperature for 24 hours before oven

curing at 80oC for additional 24 hours. Similar curing regime was employed by Tempest

(2010) but the temperature of the oven was set to 75oC. Perera at al. (2007) used a curing

schedule that involves oven curing of several specimens at 22oC, 40

oC, 60

oC, and 80

oC in

order to investigate the effect of temperature on geopolymerization and reported that at

higher temperature, the chemical reactions are accelerated leading to the formation of

higher strength geopolymer concrete. The optimal curing temperature for the formation

of geopolymer was reported to be 75oC (Pacheco-Torgal et al., 2008a).

2.2.1 Source Materials for Geopolymer Synthesis

Metakaolin, granulated blast furnace slag, and coal fly ash are the most commonly

used source materials in geopolymer synthesis. Metakaolin is obtained by the calcination

of kaolinite at high temperature (Cioffi et al., 2003) while blast furnace slag is a

byproduct of iron production. Coal fly ash on the other hand is obtained as a byproduct of

the combustion process in coal fired power plants.

Komnitsas and Zaharaki (2007) reported that geopolymer made from metakaolin

are too soft for construction purposes due to high porosity as a result of high water

requirement, thereby hindering further use of this starting material.

Blast furnace slag based geopolymer on the other hand have been reported as

containing calcium silicate hydrates (CSH) and calcium aluminosilicate hydrates (CASH)

in addition to the geopolymer phase as a result of the high content of calcium in the

starting material (Pacheco-Torgal et al., 2008b).

13

Fly ash based geopolymer provides significant advantage over other alternative

binders (Provis et al., 2009) due to the cheaper cost associated with coal fly ash when

compared to other source material like metakaolin which resulted in porous and soft

geopolymer.

In recent years, many researchers have focused on using coal fly ash as the main

aluminosilicate source for geopolymer synthesis due to its high silica content and its

abundance as a waste product. But due to variability of fly ash as a result of

characteristics such as their amorphous content, chemical composition, fineness, calcium

content and unburned organic content, producing geopolymer of consistent and

acceptable quality might be a big challenge (Tempest, 2010). These led to the

investigation of coal fly ash characteristics that can make them suitable for producing

geopolymer of acceptable quality. Khale and Chaudhary (2007) reported that fineness is

one important characteristic that affect strength development in geopolymer. Tempest

(2010) stated that loss on ignition (LOI), chemical composition, calcium and amorphous

content of the coal fly ash are also important characteristics that contribute to the quality

of the produced geopolymer. It is thus necessary to select coal fly ash that possessed

these characteristics that would lead to an acceptable geopolymer.

Coal fly ash is classified based on chemical composition as either Class F and

Class C ash (ASTM, 2008) as shown in TABLE 2-1. Class C ash are referred to as high

calcium ash because they contain more than 20% CaO, a minimum of 50% SiO2 + Al2O3

+Fe2O3 and self-cementing properties while Class F ash are referred to as low calcium

ash due to the low content of CaO (<10%), a minimum of 70% SiO2 + Al2O3 + Fe2O3 and

non self-cementing properties (ASTM, 2008). Class F fly ash is mostly used in the

14

production of geopolymer due to higher content of silica and alumina and low amount of

CaO since the amount of CaO in the starting material significantly affect the properties of

hardened geopolymer (Diaz et al., 2010). Higher content of CaO contained in Class C fly

ash would alter the microstructure of the produced geopolymer leading to formation of

more hydration products such as CSH instead of the geopolymer phase (Temuujin et al.,

2009). TABLE 2-2 shows the typical chemical composition of the two main types of coal

fly ash. For comparison purpose, this table also shows composition of Portland cement

TABLE 2-1: Chemical requirement for fly ash classification (% mass)

Class F Class C

SiO2 + Al2O3 + Fe2O3, (min %) 70 50

SO3, (max %) 5.0 5.0

Moisture content, (max %) 3.0 3.0

Loss on ignition (LOI), (max %) 6.0 6.0

Available alkali as Na2O, (max%) 1.5 1.5

Source: ASTM (2008)

TABLE 2-2: Typical chemical composition of coal fly ash and cement (%)

SiO2 Al2O3 Fe2O3 CaO MgO SO3

Class F 55 26 7 9 2 1

Class C 40 17 6 24 5 3

Portland cement 23 4 2 64 2 2

Source: ACAA (2003)

15

The total amount of some trace elements found in typical coal fly ash is presented

in TABLE 2-3.

TABLE 2-3: Typical total amount of some trace elements present in CFA

element mg/kg

As 136.2

B 900

Be 13.4

Cd 0.78

Co 50

Cr 198.2

Cu 112.8

Ni 120.6

Pb 68.2

Sb 6

Se 10.26

V 295.7

Zn 210

Source: Iwashita et al. (2007)

2.2.2 Chemistry and Reaction Mechanisms

Irrespective of the aluminosilicate source, activating solution or the curing

conditions used during geopolymer synthesis, it is believed that the reaction mechanism

involved in geopolymer formation is the same. This reaction mechanism can be grouped

into three separate but interrelated stages that include dissolution of the aluminosilicate

source by the high alkaline solution (MOH) where M+ is the alkali metal such as Na

+ or

16

K+, followed by reorientation/reorganization of the dissolved species and later

polycondensation to form the hardened geopolymer (Xu and Van Deventer, 2000;

Tempest, 2010). FIGURE 2-1 shows a simplified representation of the reaction

mechanisms involved in geopolymer synthesis.

Dissolution of the aluminosilicate is believed to be initiated by the presence of

hydroxyl ion (OH-) from the alkali hydroxide, leading to the production of aluminate and

silicate monomers (Komnitsas and Zaharaki, 2007). Production of these monomers is

strongly dependent on the reactivity of the source aluminosilicate material, type and

amount of the alkali hydroxide used. Reactivity of aluminosilicate material used in

geopolymer synthesis decreases in the following order: metakaolin > slag> fly ash>

kaolin (Panagiotopoulou et al., 2007; Tempest, 2010). According to Komnitsas and

Zaharaki (2007), higher amount of hydroxyl ions facilitate the production of different

silicates and aluminate species which would lead to further geopolymerization.

During the reorientation stage, free aluminate and silicate monomers in addition

to silicate present in the activation solution come together to form oligomers of varying

polymeric structure. These polymeric units then undergo polycondensation reaction in

which they are joined together by oxygen bond formed from the reaction of adjacent

hydroxyl ions, leading to the formation of the rigid oxygen bonded silica and alumina

tetrahedral structure of geopolymer.

The reaction mechanism revealed that the alkali hydroxide (NaOH or KOH) act as

catalyst that aid the dissolution and condensation stages. Most of the water is expelled

during the high temperature curing since they are not actually involved in geopolymer

formation (Khale and Chaudhary, 2007).

17

FIGURE 2-1: Simplified representation of geopolymer reaction mechanism.

Adapted from Duxson et al. (2007) and Yao et al. (2009)

2.2.3 Structure of Geopolymer

Geopolymer structure as suggested by Davidovits is a poly(sialate) network

consisting of silica (SiO2) and alumina (Al2O3) tetrahedral connected together by sharing

oxygen atoms (FIGURE 2-2). Sialate is an abbreviation for silicon-oxo-aluminate (Si-O-

Al) which form the basic polymeric precursor (Komnitsas and Zaharaki, 2007). Structure

of the polymeric precursor formed depends on the ratio of silica to alumina (Si/Al) in the

starting materials and can be classified according to this ratio. FIGURE 2-2 shows an

illustration of the three polymeric structures that form geopolymers.

M+ (aq)

OH- (aq)

Polycondensation

Reorientation &

reorganization

Aluminosilicate source

3D aluminosilicate network

H2O Silicate

Dissolution H2O

H2O

Aluminate and silicate

Si-O-Al= PS PSS

PSDS Polymeric units

Geopolymer

18

FIGURE 2-2: Polymeric precursor that form geopolymers.(Škvára, 2007)

Higher amount of silicate is required to form the higher order poly(sialate-siloxo)

and poly(sialate-disiloxo) structure. Increase in the Si/Al ratio can be achieved by the

addition of extra reactive silica using Na2SiO3 or silica fume in order to form these

precursors. The polymeric precursors form chain and ring network united by Si-O-Al

bridges with the silicon and aluminum atoms in 4-fold coordination with oxygen.

Metallic cations such as K and Na help keep the formed geopolymer structure neutral by

balancing the charge of Al atoms present in the structure. FIGURE 2-3 shows the

conceptual model of sodium-poly(sialate-siloxo) (Na-PSS) geopolymer.

Equation 2.1 shows the empirical formula that can be used to characterize the

formed geopolymer structure (Komnitsas and Zaharaki, 2007; Pacheco-Torgal et al.,

2008a).

Mn [-(SiO2)z-AlO2]n .wH2O (2.1)

Where M is the alkali cation, n is the degree of polycondenation, z is 1, 2 or 3, and w ≤ 3.

19

FIGURE 2-3: Conceptual structure of Na-PSS geopolymer (Škvára, 2007)

2.4 Characteristics and Application of Geopolymer

A lot of researchers have extensively studied the physical and mechanical

properties of geopolymer such as compressive strength, creep, freeze-thaw resistance,

permeability, thermal stability and shrinkage (Subaer, 2004; Hardjito and Rangan, 2005;

Rangan, 2009; Tempest, 2010) that make the material a viable alternative in a wide

application area. According to some studies, geopolymer concrete can reach 28 days

compressive strengths ranging between 70 MPa (10,000 psi) to 100 MPa (14,000psi)

(Komnitsas and Zaharaki, 2007; Zhang et al., 2008; Tempest, 2010). Somna et al. (2011)

observed that the compressive strength of the material increases with age which is similar

to the strength development in Portland cement. Result of creep and shrinkage test

performed to assess the long term performance of geopolymer showed that the material

undergo low creep and very little drying shrinkage of about 100 microstrain (µstrain)

after one year (Khale and Chaudhary, 2007; Rangan, 2008), and can withstand heat of up

to 800oC (Hardjito and Tsen, 2008). Sun (2005) observed that geopolymer does not show

20

any mass loss after about 300 freeze-thaw cycles, thus having a better freeze-thaw

performance than Portland cement. Permeability of the material was found to be between

10-9

– 10-12

cm/s (Giannopoulou and Panias, 2007) which happens to be a very low value

when compared to other cementitious material.

Due to the excellent properties possessed by geopolymer, the material has been

employed in applications that include thermal insulation, high strength concrete, and

hazardous waste management (Davidovits, 1991; Sun, 2005). Precast structures like

railway sleepers, sewer pipes, box culverts and reinforced beams have been produced

from geopolymer (Lloyd and Rangan, 2010; Tempest, 2010). Other reported areas of

geopolymer application is in waste encapsulation, high strength concrete, thermal

insulation and fire protection of structures (Davidovits, 1991; Provis and van Deventer,

2009). To demonstrate the environmental compatibility of geopolymer in the different

areas of applications, leaching of environmentally relevant trace elements are usually

studied but there are not too many studies. The following subsection summarizes relevant

leachability studies found in the literature.

2.5 Background on Leaching and Mobility of Elements

Leaching tests are techniques used to investigate environmental properties or

characteristics of any material, which can also be used for geopolymer. Leaching is a

process where constituents present in a solid material dissolves into the pore water of the

material when that material is in contact with an aqueous media. The liquid that contains

the released constituent is called the leachate. Some factors such as amount of liquid that

get in contact with the solid (L/S ratio), solubility of the elements, adsorption of the

elements, pH of the pore water, state of the material, redox conditions and reaction

21

kinetics can potentially affect leaching from any material (Bin-Shafique, 2002; Schuwirth

and Hofmann, 2006; Das, 2008).

There are a number of standard leaching test methods that have been developed to

assess mobility of elements from solid materials. A good understanding of the material

and their environment is necessary in order to choose the most appropriate leaching test.

These test methods can be categorized into three types as shown in TABLE 2-4. In

equilibrium oriented leaching test methods, equilibrium between the material and

leaching solution is achieved by agitation of the mixture, while capacity oriented leaching

test examines the maximum amount of each contaminants that can be released from the

material under the worst case scenario (Schwantes and Batchelor, 2006). Dynamic

oriented tests are used to investigate the mechanism responsible for release of

contaminants from the solid material.

The most widely used leaching test methods in the United States are TCLP, WLT,

SPLP, EP Tox, while the use of tests such as pH stat, NEN 7341, 7343 and 7345 are

common in Europe. All the different tests are used to assess leachability of different

material at different exposure scenarios. Results from the various leaching tests are

expressed either as leachates concentration (mg/l) or as constituent released in mg/kg dry

mass for granular material and mg/m2 for the monolith materials.

2.5.1 Mobility of Elements from Geopolymer

Leaching test methods such as TCLP, NEN 7375, NEN 7341 have been used to

assess mobility of elements from geopolymer (Bankowski et al., 2004; Izquierdo et al.,

2010), NEN 7341 have been specifically used to assess the mobility of oxyanion forming

elements.

22

TABLE 2-4: Summary of various leaching test methods

TABLE 2-4 (continued)

Type Leaching test Leaching

medium

L/S Particle

size

Leaching

duration

Reference

Equilibrium

oriented

Toxicity

Characteristics

Leaching

Procedure

(TCLP)

Acetic

acid

20 <9.5mm 18 hours Schwantes

and

Batchelor

(2006)

Extraction

Procedure

Toxicity test

(EP Tox)

0.04 M

acetic

acid (pH

5)

16 <9.5mm 24 hours Schwantes

and

Batchelor

(2006)

Water Leach

Tests (WLT)

Deionized

water

20 <9.5mm 18 hours ASTM

(2006c)

Equilibrium

Leach Tests

(ELT)

Deionized

water

4 <150 µm 7 days Schwantes

and

Batchelor

(2006)

Multiple

Extraction

Procedure

(MEP)

0.04 M

acetic acid

(pH 3)

20 <9.5 mm 24 hours

per stage

(9

extractio

n stages)

USEPA

(1986)

23



medium

L/S Particle

size

Leaching

duration

Reference

Synthesis

Precipitation

Leach

Procedure

(SPLP)

Deionized

water

adjusted to

pH 4-5

20 <9.5 mm 18 hours USEPA

(1994)

pH Static

leaching test

Deionized

water

adjusted to

pH 4-13

by HNO3

and NaOH

5 <4 mm 24 hours Schwantes

and

Batchelor

(2006)

USEPA draft

method 1313

Deionized

water

adjusted to

pH 3-13

by HNO3

and NaOH

10 <5 mm 24 hours USEPA

(2009b)

Capacity

oriented

Availability

test

Two steps:

pH 4 and

7

100 <150 µm 3 hours

each step

EA

(2005a)

24



medium

L/S Particle

size

Leaching

duration

Reference

Nordtest

availability test

Two steps:

pH 4 and

7

100 <125 µm 1st : 3

hours

2nd

: 18

hours

Nordtest

(1995)

Dynamic

oriented

American

Nuclear

Society (ANS)

leach test 16.1

Sequential

extraction

by

deionized

water

5 -

10

Monolith Sample

at 1, 2, 4,

8, 16, 32,

64 days

Schwantes

and

Batchelor

(2006)

Column test

(NEN 7343)

Systematic

L/S ratio

increase

0.1

-10

<4 mm Schwantes

and

Batchelor

(2006)

Tank test Deionized

water at

pH 4

Monolith Samples

collected

at 0.25,

1, 2.25,

4, 9, 16,

36, 64

days

EA

(2005b)

25



medium

L/S Particle

size

Leaching

duration

Reference

USEPA draft

method 1315

Deionized

water

Monolith Samples

collected

at 0.08,

1, 2, 7,

14, 28,

42, 49

and 63

days

USEPA

(2009c)

2.6 Oxyanion Forming Trace Elements

Oxyanions are negatively charged polyatomic species that contain oxygen ions

(Cornelis et al., 2008). Common oxyanions are SO42-

, NO3-, AsO4

3-, and PO4

3-. Trace

elements that form oxyanionic species include boron (B), arsenic (As), chromium (Cr),

selenium (Se), vanadium (V), molybdenum (Mo), tungsten (W) and antimony (Sb).

These elements can form different species of oxyanion depending on pH and redox

potential. Among the elements, As, Cr and Se are considered elements of concern due to

their toxicity and mobility at alkaline pH (Zhang, 2000; Wang, 2007; Izquierdo et al.,

2010), and are listed by the USEPA as priority pollutants in drinking water (Min, 1997;

USEPA, 2009a). Since most elements that form oxyanion exhibit similar behavior,

understanding the behavior of As, Cr and Se would lead to understanding the behavior of

the other elements.

26

2.6.1 Occurrence and Chemistry of Arsenic, Chromium and Selenium

Arsenic is a metalloid found in group 15 and period 4 of the periodic table, it

occurs in association with sulfur containing minerals such as realgar (AsS), orpiment

(As2S3) or arsenopyrite (FeAsS) (Magalhães, 2002). The element is released into the

environment via weathering, volcanism, agricultural applications and waste stream of

industrial process with high concentration in coal fly ash (Jackson, 1998; Moon et al.,

2004). Its abundant in the earth crust is between 1.5 - 2.0 ppm (NAS, 1977).

Selenium is a non-metallic element found in group 16 and period 4 of the periodic

table. This element is not abundant in the earth crust, comprising only 0.05 ppm of the

earth crust (Zhang, 2000). Selenium is a micronutrient required by humans and animals

to maintain good health, and considered a necessary constituent of human diets for many

years (B'Hymer and Caruso, 2006). Deficiency of these micronutrient might inhibit

growth and too much of it can also lead to death. Bond (2000) stated that due to the

narrow range between the beneficial and harmful level of selenium, the USEPA listed the

element among element of concern in drinking water and specified the maximum amount

of the element allowed in drinking water (USEPA, 2009a).

Chromium is a transition element that occur in group 6 and period 4 of the

periodic table, it is the 21st most abundant element in the earth crust with concentration of

about 100 ppm (Barnhart, 1997). It occurs in nature as the mineral chromites (FeCr2O4)

and crocoites (PbCrO4) (Zhang, 2000). The chemical properties and maximum

contaminant level (MCL) of these elements are summarized in TABLE 2-5.

27

TABLE 2-5: Chemical properties and MCL of As, Cr and Se.

Elements Group Atomic

no

Atomic

mass

Electron

configuration

Oxidation

states

MCL

µg/l

As 15 33 74.92 [Ar]4s23d

104p

3 -3, 0,+3,+5 10

Cr 6 24 52.00 [Ar]3d5 4s

1 0,+3,+6 100

Se 16 34 78.96 [Ar]4s2 3d

104p

4 -2,0, +4,+6 50

Sources: Zhang (2000); Paoletti (2002); Cornelis et al. (2008); USEPA (2009a)

In nature, Arsenic (As) occurs mainly in the As+3

(arsenite) and As+5

(arsenate)

oxidation states (Alexandratos et al., 2007), with As+3

being more mobile and reported to

be 25 - 60 times more toxic than As+5

(Moon et al., 2004). Cr+3

and Cr+6

oxidation state

are the most abundant form of chromium (Cr) in nature, with Cr+6

being about 100 times

more toxic and soluble than Cr+3

(Shtiza et al., 2009). Selenium (Se) exist in nature as

Se+4

and Se+6

forming SeO32-

(selenite) and SeO42-

(selenate) oxyanionic species (Bond,

2000).

2.6.2 Environmental Aspect and Toxicity of As, Cr and Se

Oxyanions of As, Cr and Se are very mobile in high alkaline environment and

have low mobility in the acidic environment due to bonding with metal oxyhydroxides

(Zhang, 2000). TABLE 2-6 shows the redox states of As, Cr and Se oxyanionic species

and their form of occurrence in alkaline environment. In this type of environment, As+3

,

As+5

, Cr+3

, Cr+6

, Se+4

and Se+6

are the most predominant redox state because they are

more soluble than those occurring in their elemental and reduced states (Cornelis et al.,

2008).

28

TABLE 2-6: Redox states of the oxyanions in alkaline environment

Element Oxidation states

-2 0 +3 +4 +5 +6

As As0 H2AsO3

- AsO4

2-

Cr Cr0 Cr(OH)4

- CrO4

2-

Se HSe- Se

0 SeO3

2- SeO4

Source: Cornelis et al. (2008)

Arsenic in the trivalent form is more toxic and a known carcinogen that causes

cancer of the liver skin and kidney (Magalhães, 2002). Chromium on the other hand is

most toxic in the hexavalent form and possess mutagenic properties that can damage

circulatory system and cause carcinogenic changes in human (Soco and Kalembkiewicz,

2009).

2.7 Methods of Immobilizing the Leaching of Oxyanion Elements

According to Cornelis et al. (2008), calcium containing mineral phases and

metalate precipitation exert control over the leaching of oxyanions. The authors stated

that minerals such as CSH, ettringite, monosulfoaluminate and hydrocalumite can

partially or fully replace their anions (OH- or SO4

2-) with oxyanions thereby causing

reduction in mobility of these oxyanion forming elements (Cornelis et al., 2008). Several

studies have demonstrated this by showing that mobility of As and other oxyanions in

alkaline environment can be reduced by the addition of lime, which would result in the

formation of either an insoluble calcium precipitate or oxyanion substituted calcium

mineral phases (Moon et al., 2004; Zhu et al., 2006; Alexandratos et al., 2007; Wang et

al., 2007).

29

2.7.1 Incorporation into Ettringite Structure

Ettringite is a hydrated calcium aluminum sulfate hydroxide mineral with

chemical formula (Ca6Al2(SO4)3(OH)12•26H2O) and a needle like crystal structure

depicted in FIGURE 2-4. It is an example of an AFt (alumina ferric oxide tri sulfate)

phase present in cement system whose structure favors extensive ionic substitution

potential that can make the immobilization of oxyanions possible. Substitution of SO42-

present in ettringite structure by oxyanions such as CrO42-

, AsO43-

, SeO42-

, CO32-

, and

NO3- have been reported by Bone et al. (2004) and Cornelis et al. (2008). FIGURE 2-5

depicts an oxyanion substituted ettringite crystal structure.

FIGURE 2-4: Schematics of ettringite crystal structure (Klemm, 1998)

30

FIGURE 2-5: Oxyanion substituted ettringite structure (Cornelis et al., 2008)

2.7.2 Incorporation into Hydrocalumite Structure

Hydrocalumite is an anionic clay mineral composed of stacked portlandite-like

octahedral layers where one third of the Ca2+

sites is occupied by Al3+

(Zhang and

Reardon, 2003). The mineral has a chemical formula Ca4Al2(OH)2(OH)12•6H2O and

structure shown in FIGURE 2-6 which have interlayer water molecule and anions.

FIGURE 2-6: Schematics of hydrocalumite structure (Zhang and Reardon, 2003)

Zhang and Reardon (2003) reported that the substitution of Ca2+

with Al3+

result

in net positive charges on the layers that enable incorporation of anion or oxyanion (Xn-

)

in order to balance the charges on the octahedral layers. Zhang and Reardon (2005)

31

demonstrated the incorporation of oxyanions such as Cr and Se which led to reduction in

leaching of the elements.

2.7.3 Incorporation into Monosulfoaluminate Structure

Monosulfoaluminate is a mineral that can be found in products of cement

hydration, it is an AFm (aluminiate ferric oxide monosulfate) phase that has chemical

formula Ca4Al2SO4(OH)12•6H2O and a lamellar hexagonal platey structure shown in

FIGURE 2-7.

FIGURE 2-7: Schematics of monosulfoaluminate structure (Baur et al., 2004)

Monosulfoaluminate also exhibits similar anionic substitution as ettringite; in this

case the SO42-

and OH- in the structure are replaced by anions or oxyanions. Saikia et al.

(2006) reported that oxyanions can also be incorporated between layers of

monosulfoaluminate structure serving as interlayer anions.

2.7.4 Incorporation into Calcium Silicate Hydrate (CSH)

CSH is a principal hydration product formed during the hydration of alite and

belite phases of Portland cement (Gougar et al., 1996). According to Yip and van

Deventer (2003), CSH gel coexists with geopolymeric gel in geopolymer system if there

is enough calcium present in the system. This CSH gel has positive charged surfaces

which have the potential for adsorbing oxyanions such as, AsO43-

, AsO33-

, SeO32-

and

32

CrO42-

(Cornelis et al., 2008). The successful immobilization of Cr by CSH was reported

by Gougar et al. (1996).

2.7.5 Formation of Precipitates

At pH of around 12.6, the formation of calcium metalate precipitates is reported

to be effective at immobilizing oxyanion forming elements (Bone et al., 2004).

According to Moon et al. (2004), formation of calcium metalate precipitate have been

successful at immobilizing arsenic which occurs in the As+3

form as HAsO32-

and As+5

as

HAsO42-

. Magalhães (2002) stated that calcium arsenates such as weilite (CaHAsO4),

pharmacolite (CaHAsO4•2H2O), haidingerite (CaHAsO4•H2O), phaunouxite

(Ca3(AsO4)2•11H2O) are particularly formed.

2.8 Mineralogical and Microstructural Characterization of Geopolymer

X-Ray diffractometer (XRD) analysis is used to analyze mineral phases present in

solid materials. XRD analysis of geopolymer made from fly ash shows the presence of

quartz (SiO2), mullite (Al6Si2O13) zeolites such as hydroxysodalite (Na4Al3Si3O12OH)

and herchelite (NaAlSi2O6•3H2O), and a diffuse halo peaks at 2θ angle of between 20o –

40o (Fernández-Jiménez and Palomo, 2005; Fernández-Jiménez et al., 2007; Zhang et al.,

2009; Guo et al., 2010). This suggests that geopolymer contains both crystalline and

amorphous (non crystalline) phases.

Microstructure of geopolymers have been observed by a lot of researchers using

the scanning electron microscope (SEM) which is an instrument used to produce high

resolution image of sample surfaces (Das, 2008). The structure of fly ash based

geopolymer reveals that the material consists of crust of shapeless reaction product and

presence of unreacted spherical fly ash particles depending on the degree of reaction

33

(Fernández-Jiménez and Palomo, 2009). Some of these unreacted fly ash particles are

sometimes covered with the reaction products.

2.9 Geochemical Modeling

Geochemical modeling tools have been increasingly used to assess environmental

impact and speciation of elements from materials (Halim et al., 2005) in order to answer

environmental questions such as: (1) How fast contaminants move and when it will reach

a certain point? (2) Whether the concentration of the contaminant exceeds regulatory

limits? (3) What processes will hinder or immobilize the contaminants? (4) What is the

state of the particular site under investigation? Geochemical modeling have been used in

the assessment of high level nuclear waste repositories, exploratory and feasibility studies

of mining sites, and speciation of elements from the interaction between landfill leachates

and liners (Zhu and Anderson, 2002).

According to Zhu and Anderson (2002), geochemical models are divided into

speciation-solubility model, reaction-path model and reactive transport model based on

their level of complexity. Speciation-solubility models perform batch calculations and

provide no spatial or temporal information about the contaminant, reaction path models

on the other hand are used to simulate successive reaction steps in response to mass or

energy flux thereby providing some temporal information about the progress of the

reaction. Reactive transport models are very complex models that provide both temporal

and spatial information of the chemical reactions. The most basic and least expensive

models belong to the speciation-solubility model group, they are suitable for answering

questions about concentration of constituents species present in an aqueous solution, and

their saturation states with respect to various minerals in the aqueous system. Common

34

speciation-solubility models are MINTEQA2, MINEQL+, geochemist‘s workbench,

EQ3/EQ6, SOLMINEQ.88,WATEQ4F and PHREEQC (Zhu and Anderson, 2002; Zhu,

2009). All these models involve batch calculations and serves as the basis for the reaction

path and reactive transport models (Zhu and Anderson, 2002).

PHREEQC (Parkhurst and Appelo, 1999) is the most widely used speciation-

solubility modeling tools with capability that includes performing speciation and

saturation index calculations, batch and one dimensional (1D) reaction transport

calculation, and inverse mass balance modeling (Parkhurst and Appelo, 1999; Zhu and

Anderson, 2002; Bone et al., 2004). According to Parkhurst and Appelo (1999), the

acronym PHREEQC stands for pH values (PH), redox (RE), equilibrium (EQ), and C

programming language (C) which are the most important parameters in the model. The

model utilizes solubility products (Ksp) of aqueous solution, minerals and solid solutions

to calculate the equilibrium state of the system under specific conditions using databases

included in the program which contains information on equilibrium constants and

properties of the different species of minerals, elements and solid solution.

Equilibrium state between the aqueous solution and mineral phases present is

evaluated based on value of the calculated saturation indexes (SI) of the system which is

obtained by relating the ion activity product (IAP) observed in solution and the

theoretical solubility product (Ksp) using Equation 2.2 (Appelo and Postma, 2005;

Andrews, 2007).

SI= log (IAP/Ksp) (2.2)

Andrews (2007) defined SI as the concentration at which dissolved concentration

of mineral components is saturated with respect to the solution. A negative SI value (SI <

35

0) indicates that the solution is undersaturated with respect to the mineral thereby making

the mineral dissolve, positive SI value (SI > 0) means that the solution is supersaturated

with respect to the mineral and the mineral will precipitate, and when SI equals zero, the

solution is in equilibrium with respect to a mineral (Andrews, 2007; Zhu, 2009). For SI

close to zero, the phase is in near equilibrium state with the solution and can be

considered as the controlling phase (Schiopu et al., 2009).

2.10 Summary

Despite the growing interest in geopolymer technology, there have been few

studies on the environmental characterization of the material. These studies have revealed

that geopolymer could leach out elements that include As, Cr and Se which are

considered priority pollutants in drinking water by the USEPA.

According to Cornelis et al. (2008), mobility of oxyanion forming elements can

be reduced using calcium containing mineral phases and metalate precipitation. Ettringite

was found to favor ionic substitution in which the SO42-

present in its structure is replaced

by the oxyanions (Bone et al., 2004). It was also reported by Zhang and Reardon (2003)

that the net positive charge on hydrocalumite structure can enable incorporation of

oxyanions to balance the charge on the mineral. Monosulfoaluminate was also found to

exhibit similar ionic substitution as ettringite (Saikia et al., 2006). In this case, the SO42-

and OH- in the structure are replaced by the oxyanions. Formation of calcium metalate

can also reduce the mobility of the oxyanion forming elements (Bone et al., 2004; Moon

et al., 2004). CSH which coexists with geopolymer gel also have potential for absorbing

oxyanions thereby reducing the elements mobility. It is evident from the literature that

calcium containing mineral phases can successfully lead to a reduction in mobility of

36

oxyanion forming elements which exist in different oxidation states, and whose mobility

and toxicity depends on the specie of the element present in any solution. Geochemical

modeling has been identified as a tool that can be used to assess the speciation of these

elements. PHREEQC, a widely used speciation-solubility modeling tool was considered

an ideal tool for determining the speciation of elements such as As, Cr and Se.

This dissertation would in addition to investigating the mobility leaching

mechanisms of oxyanions (As, Cr, Se) focus on using calcium containing mineral phases

in reducing the mobility of the elements from fly ash based geopolymer concrete, and the

use of PHREEQC/PHREEPLOT to predict the species of each element that would be

released from the material.

CHAPTER 3: EXPERIMENTAL PROTOCOL

3.1 Research Approach

The research approach employed is a quantitative approach which entails the use

of experimental methods to test the stated hypotheses. This approach involves making

geopolymer concretes with varying amount of hydrated lime added during synthesis,

subjecting the material to established experimental techniques at the service life and end

of life of the material life cycle. Cementitious materials like geopolymer concrete exist in

monolith form during its service life and in granular / crushed form at end of life.

Appropriate test methods are chosen for the different stage of the material life cycle.

3.2 Materials

3.2.1 Coal Fly Ash (CFA)

The CFA used in this study was obtained from a coal fired power plant in

Southeastern United States and classified as a Class F ash (as per TABLES 2-1 and 2-2)

based on its chemical composition. The material consists of high amount of oxides of

silicon and aluminum and a low amount of calcium oxide making it a suitable source

material for geopolymer synthesis.

3.2.2 Silica Fume (SF)

The SF used in this study was purchased from Ohio valley alloy services and

contains 98% amorphous silica and meets standard specification for silica fume used in

cement (ASTM, 2010b). Since higher amount of silica (SiO2) is required for geopolymer

38

synthesis, silica fume (SF) was added to increase the silica to alumina ratio (Si/Al) in

order to aid the formation of higher order poly(sialate-siloxo) and poly(sialate-disiloxo)

geopolymer structure.

3.2.3 Sodium Hydroxide (NaOH)

Sodium hydroxide (NaOH) is one of the components in the activating solution

responsible for dissolution of the starting fly ash during geopolymer synthesis. The

NaOH used is a commercial grade NaOH pearls with 98% purity.

3.2.4 Hydrated Lime (Ca(OH)2)

High calcium hydrated lime (Ca(OH)2) supplied by UNIVAR was used in the

study. The hydrated lime has about 95% Ca(OH)2 content with no Mg(OH)2 which

conforms to the specification of type N hydrated lime used in mortar and Portland cement

concrete (ASTM, 2006b).

3.2.5 Aggregates

The coarse (CA) and fine (FA) aggregates used in the study are the same type

used in making Portland cement concrete. The CA and FA are respectively a ⅜ inches

granite stone and silica sand. The aggregates were used in the saturated surface dry (SSD)

condition.

3.3 Experimental Method

The experimental method is divided into five different phases that are

summarized in TABLE 3-1. It consists of the various tasks that are completed to achieve

the research objectives and test the stated hypotheses. Detailed information of the

different experimental phases is presented in subsequent chapters of this dissertation.

Since the material exist in the monolith form during its service life and in crushed or

39

granular form at end of life, some of the geopolymer concretes were tested in the

monolith form and others in the granular/powder form.

TABLE 3-1: Experimental phases for the dissertation


Phase Task description

I Characterization of the materials / geopolymer products

a. XRF analysis

b. ANC/BNC test

a. Stabilized pH and moisture content

b. Bulk density and PSD

II Synthesis of fly ash geopolymer concretes and sample preparation

a. Geopolymer concrete without lime

b. Geopolymer concrete with lime

c. Crushing and sub sampling

d. Grinding and sieving

III Laboratory leaching test methods

a. Availability test

b. Tank leaching test

c. pH stat test

d. Water leach test

IV Mineralogical and microstructural characterization

a. XRD analysis

b. SEM/EDX analysis

40


Phase Task description

V Geochemical modeling using PHREEQC/PHREEPLOT

a. Speciation modeling

b. Model simulation results and interpretation

3.4 Quality Assurance and Quality Control

Proper sampling technique is used to obtain representative samples of the

geopolymer concrete. Dry granular samples were placed in ziplock bags and stored in a

dry storage container. All samples were immediately labeled to avoid confusion with

other samples. To ensure accuracy and precision in all measurements, all the analysis

except the XRD and SEM are performed in duplicate or triplicate. Blank analyses are

also included in some analytical methods using the same reagents and equipments but

without the samples, this will confirm the presence of any contamination during the

analytical methods.

All glasswares and labwares were acid washed and rinsed three times with

deionized water (DI) before each use. Only recently calibrated scales are utilized in all

weight measurements. All equipments are properly cleaned before testing another sample

to avoid cross contamination of samples. All samples are stored according to standard

storage requirements for each type of sample; liquid for cation analysis are acidified to

pH < 2 to minimize metal cations from precipitating and adsorption onto the storage

container wall (USGS, 1998) while liquid samples for anion analysis are not acidified.

All the liquid samples are then stored in a refrigerator maintained at 4oC or less.

41

3.5 Statistical Analysis of Data

All raw data obtained from the analysis are transformed into easily

understandable data form. The mean and standard deviation of all duplicate and triplicate

measurements are determined. Non parametric statistical analysis such as Kruskal-Wallis

test was used to statistically compare the results obtained from the four geopolymer

concrete samples. Tukey‘s HSD pairwise comparison was used to determine which

geopolymer concrete sample is significantly different from the other. JMP statistical

software version 9.0 by SAS was utilized in all statistical analysis at a 95% confidence

interval.

3.6 Pilot study

This section describes preliminary research studies that was completed on fly ash

based geopolymer concrete and paste in order to become familiarize with the synthesis of

the geopolymer and conducting the experimental methods. Majority of the work have

been on geopolymer paste. Geopolymer concrete samples were later produced with

recycled concrete aggregate (RCA) replacing some of the coarse aggregate. RCA was

incorporated into geopolymer concrete to create an outlet for using demolished concrete

waste and study how excess calcium in the RCA affect mobility of elements from the

produced geopolymer. Most of the results from the preliminary investigation have been

presented in conferences (Sanusi and Ogunro, 2009; Ogunro and Sanusi, 2010; Sanusi et

al., 2011).

3.6.1 Element Mobility from Fly Ash Based Geopolymer Paste

Mobility of 29 elements from geopolymer paste was studied using short term (6

hours) pH leaching test (Ogunro and Sanusi, 2010). In this investigation, geopolymer

42

paste whose components by weight include 67% Class F coal fly ash, 10% NaOH and 8%

SF was produced by mixing activating solution (dissolving SF in hot concentrated

NaOH) with CFA. The mixture was cast in cylindrical mold and cured in the oven at

75oC for 24 hours. Compressive strength of the cylinders was determined at 28 days, the

mortar crushed and pulverized to fine particles required for the pH leaching test. The pH

dependence leaching test used was performed at a liquid to solid (L/S) ratio of 10 with

continuous pH control based on a slight modification of the European standard pH test

CEN/TS 14997 (CEN, 2006). In the test method, the leaching solution pH was

continuously controlled to pH 3, 5, 7, 9, 11 and 13 using HNO3 or NaOH for 6 hours, and

the leachates filtered using 0.45µm membrane filter.

The results obtained reveals that mobility of elements varies across the pH range.

Elements such as barium (Ba), beryllium (Be), cobalt (Co), copper (Cu), manganese

(Mn), zinc (Zn), iron (Fe), magnesium (Mg), boron (B), strontium (Sr), lithium (Li) and

nickel (Ni) display high mobility at low pH which decreases as the pH increases from

acidic to the alkaline pH (FIGURE 3-1 and 3-2). Elements with very high mobility from

the geopolymer paste include aluminum (Al), sodium (Na), silicon (Si), calcium (Ca) and

potassium (K) (FIGURE 3-3) due to their high solubility during the geopolymerization

process. The mobility of these elements is almost constant at the acidic pH range and

increases gradually in the alkaline pH. Mobility of silver (Ag), cadmium (Cd), lead (Pb),

antimony (Sb), tin (Sn) and thallium (Tl) is very low across the pH range. The oxyanion

forming elements such as arsenic (As), selenium (Se), vanadium (V), molybdenum (Mo)

and chromium (Cr) on the other hand display lower mobility in the acidic pH, their

highest mobility occurs at pH between 9 and 11(FIGURE 3-4).

43

FIGURE 3-1: Mobility of elements from the geopolymer paste (category 1)


0

5

10

15

20

25

0 2 4 6 8 10 12 14

Con

centr

atio

n (

mg/k

g)

pH

Ba Be Co Cu Mn Zn

0

50

100

150

200

250

300

0 2 4 6 8 10 12 14

Conce

ntr

atio

n (

mg/k

g)

pH

Fe Mg B Sr Li Ni

44



The preliminary study reveals that depending on the pH of the environment where

geopolymer is been utilized, different elements can potentially leach out. In an acidic

environment, Ba, Be, Co, Cu, Mn, Fe, Mg, B, Sr, Li and Ni are elements that would leach

0

5000

10000

15000

20000

25000

0 2 4 6 8 10 12 14

Conce

ntr

atio

n (

mg/k

g)

pH

Al Na Si Ca K

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12 14

Conce

ntr

atio

n (

mg/k

g)

pH

As V Se Ti Mo CR

45

out more while As, V, Se, Tl, Mo and Cr would leach out more in an alkaline

environment similar to the pH of the pore solution within the geopolymer (pH > 9).

Consequently, the focus of this research is to investigate the leachability of some target

oxyanions (As, Se and Cr).

3.6.2 Leaching of Oxyanion Forming Elements from Fly Ash Based Geopolymer Paste

Based on the results obtained from the pH leaching test (Section 3.6.1) which

showed that oxyanion forming elements leach more at the alkaline pH, there is thus a

need to find the most appropriate leaching test that can effectively predict the maximum

leaching of these elements. The Dutch availability test happens to be the most widely

used test for this type of environmental assessment. The test is a two step extraction

procedure conducted at pH 7 and pH 4, with the extraction step conducted at pH 7

designed to determine the leaching of oxyanion forming elements. But with the higher

mobility of the oxyanion forming elements at alkaline pH, the conventional availability

test conducted at pH 7 would underestimate their leaching, thereby creating an

opportunity for modification of the test to reflect the alkaline pH of the geopolymer

(Sanusi and Ogunro, 2009).

The aim of the study is to determine which availability test method is better for

oxyanion element leaching. Geopolymer paste was produced from CFA, NaOH and SF

using the mix design presented in section 3.6.1, and oven cured for 24 hours before

curing at ambient temperature until the 28 days test date. The geopolymer specimens

were crushed, pulverized and size reduced to particles <150µm required for the

availability test. The availability test (NEN 7341) and a modification of the test (MNEN)

was used to determine the leaching of As, Se and Cr from the geopolymer paste. TABLE

46

3-2 shows the experimental conditions for the two tests. In situations where pH needs to

be controlled, HNO3 was used to control the pH for the duration of the extraction step or

procedure.

TABLE 3-2: Experimental conditions for the availability tests

Test pH conditions Test duration

MNEN

1st step No pH control 18 hours

2nd

step 4 ± 0.5 3 hours

NEN

1st step 7 ± 0.5 3 hours

2nd

step 4 ± 0.5 3 hours

Results obtained from the investigation were statistically compared using the

Wilcoxon signed rank test at 95% confidence interval (α=0.05). The hypotheses tested in

this preliminary study is that standard leaching test method conducted at neutral pH is

adequate for predicting the leaching of oxyanion forming elements (As, Cr, Se). The null

(Ho) and alternative (Ha) hypothesis utilized in the statistical comparison are listed

below:

Ho: The concentrations of As, Cr and Se measured in the NEN 7341 and MNEN are

not different (NEN 7341 = MNEN). The test methods are the same.

Ha: The concentrations of As, Cr and Se measured in the NEN 7341 are generally less

than the concentration measured in MNEN (NEN 7341 < MNEN). The MNEN

test method gave results with higher measured concentrations.

The statistical comparison showed that there is no significant difference between

the results from the two test methods for As (p-value=0.6250), Se (p-value=0.6250), and

Cr (p-value=0.1250). In conclusion, it was observed that although the NEN 7341 was

47

conducted at pH 7, it is still effective at predicting the leaching of the oxyanion elements

such as As, Cr and Se and there is no need to consider a modification of the test to reflect

the alkaline nature of the geopolymer (Sanusi and Ogunro, 2011b).

3.6.3 Mitigating Leachability from Geopolymer Concrete using RCA

Based on extensive literature on the immobilizing oxyanions (presented in Section

2.7), this study focused on the use of additional calcium in geopolymer which would lead

to the formation of calcium containing mineral phases needed for the reduction in

mobility of oxyanion forming elements (Sanusi et al., 2011). Three mix of geopolymer

concretes were made using CFA, SF, natural coarse and fine aggregate, with recycled

concrete aggregate (RCA) used as partial replacement for the coarse aggregate. The

mixes made are: GC - geopolymer concrete with 0% RCA, RC10 – geopolymer concrete

with 10% RCA, and RC50- geopolymer concrete with 50% RCA. The RCA was used to

respectively replace 10% and 50% of the coarse aggregate content in the RC10 and RC50

concrete samples.

The CA, FA, CFA and RCA were mixed in a rotary mixer for 3 minutes before

adding the activating solution and the mixture was further mixed for an additional 3

minutes. The concrete was cast in cylindrical mold, aged for 24 hours before oven curing

at 75oC for another 24 hours. Compressive strength of the concretes were determined at

28 days, and the concretes crushed and size reduced to particle < 150µm. Dutch

availability test was used to assess the mobility of As, Cr and Se from the different

geopolymer concrete mix.

The compressive strength result (FIGURE 3-5) showed that replacing coarse

aggregate with RCA lead to increase in strength of the geopolymer concrete. The

48

leaching result presented in FIGURE 3-6 reveals that there is a reduction in mobility of

As and Se as the replacement of coarse aggregate with RCA increases. The study showed

that the use of RCA which contains soluble calcium would lead to an increase in strength

of geopolymer concrete and a reduction in mobility of the oxyanion elements analyzed.

FIGURE 3-5: Compressive strength of the fly ash based geopolymer concretes

FIGURE 3-6: Concentration of the leached oxyanion forming elements

0

10

20

30

40

50

60

GC RC10 RC50

Com

pre

ssiv

e st

rength

(M

Pa)

Geopolymer sample

0

2

4

6

8

10

12

14

16

GC RC10 RC50

Conce

ntr

atio

n (

mg/k

g)

Geopolymer sample

As Cr Se

49

3.6.4 Influence of Lime on Strength and Mobility of Elements from Geopolymer Paste

Motivation for studying the influence of lime on strength and mobility of

elements from geopolymer paste came from findings in the literature that Calcium

containing mineral phases can be used to reduce mobility of oxyanion elements and from

the result obtained from using RCA as partial replacement in geopolymer concrete

presented in section 3.6.3. In this particular study, two geopolymer mix (GPC and GP3)

were made using CFA, SF, NaOH and Ca(OH)2, with the GP3 mix having 3% additional

calcium in the form of Ca(OH)2 (Sanusi and Ogunro, 2011a). The CFA was mixed with

the activating solution which contains SF dissolved in hot concentrated NaOH. The

resulting geopolymer paste was cast in cylindrical mold and cured in the oven for 24

hours at 75oC.

Compressive strength of the geopolymers were determined after 28 days of

curing, and the tank leaching test based on the USEPA draft method 1315 (USEPA,

2009c) was used to investigate the mobility of elements from the monolithic geopolymer

samples. In this leaching test, the monolithic samples were submerged in deionized water

for 64 days in a tightly sealed container. The water was removed and replenished at nine

successive leaching intervals as specified by the leaching standard.

The result showed that there is an observed reduction in compressive strength of

the geopolymer mix made with extra Ca(OH)2 (FIGURE 3-7). The compressive strength

of the geopolymer paste dropped from 52 MPa in the GPC to 45 MPa for GP3, a 13%

reduction in the strength. It is suspected that the extra calcium result in formation of

calcium silicate hydrate (CSH) that hindered the geopolymerization process. Inductively

coupled plasma mass spectrometer (ICP-MS) was used to determine the concentration of

50

16 elements in the leachates collected from the leaching test. It was observed that there

was a slight reduction in the mobility of As, B, Ba, Cr, Fe, Mg, Mo, Se, S, and Zn from

GP3 mix when compared with GPC (FIGURE 3-8) suggesting that the added calcium

resulted in slight leachability reduction. On the basis of these preliminary findings, a

more rigorous and targeted study was developed to test all the hypotheses stipulated in

chapter one.

FIGURE 3-7: Compressive strength comparison for two geopolymer paste mixes

0

10

20

30

40

50

60

GPC mix GP3 mix

Aver

age

28 d

ay c

om

pre

ssiv

e st

rength

(M

Pa)

Geopolymer paste

n= 3

51

0.1

1

10

100

1000

10000

100000

Al As B Ba Ca Cr Cu Fe Mg Mn Mo Na Se Si V Zn

Cu

mu

lati

ve a

mo

un

t le

ach

ed

(m

g/m

2)

Elements

GPC GP3

FIGURE 3-8: Cumulative amount of elements leached from the two geopolymer paste

CHAPTER 4: SYNTHESIS OF GEOPOLYMER CONCRETE AND SAMPLE

PREPARATION

4.1 Synthesis and Preparation of the Geopolymer Concretes

Geopolymer concrete samples were made using the same mix design developed

by Tempest (2010). The mix design used in this study is presented in TABLE 4-1. This

mix was modified by incorporating varying amount of hydrated lime (0%, 0.5%, 1.0%,

and 2.0%) which slightly increased the mass of the total components without changing

the proportion of NaOH (10% NaOH/CFA) and SF (7.5% SF/CFA) in the mix. Due to

the added lime, the water to cementitious material (w/c) ratio varies from 0.364 to 0.358.

According to the mix design, the aggregates (CA and FA) make up 68% of the total

geopolymer concrete mix, while the SF content is 1.6%, NaOH is 2.1%, water and CFA

content are respectively 8.9% and 21%.

The activating solution required for the geopolymer synthesis was prepared the

previous day by dissolving SF in hot concentrated NaOH solution and allowing the

mixture to equilibrate in the oven for 24 hours. The geopolymer concretes were made in a

conventional concrete batch mixer, the FA, CA, Ca(OH)2 and CFA was thoroughly

mixed in a rotary mixer for 3 minutes, and the liquid component (activating solution)

later added and mixed together for additional 2 minutes. The resulting geopolymer

concrete was cast into 76.2mm (3 inches) by 152.4mm (6 inches) plastic cylindrical

molds in three layers, and consolidated by rodding each layer 25 times. Eighteen (18)

53

cylinders were made for each geopolymer concrete mix. After aging for 24 hours at

ambient temperature, nine cylinders were cured in the oven at 75oC for 24 hours while

the remaining nine samples cured without heat at room temperature. The concrete

samples were removed from the molds after 48 hours of casting and allowed to aged for 7

and 28 days at room temperature (25oC).

TABLE 4-1: Mix design for the geopolymer concrete (kg/m3)

Mix Ca(OH)2 (%) CFA FA CA SF NaOH H2O w/c

GPC 0 (0) 483 773 774 36 48 207 0.364

GP1 3 (0.5) 483 773 774 36 48 207 0.363

GP2 5(1.0) 483 773 774 36 48 207 0.361

GP3 10(2.0) 483 773 774 36 48 207 0.358

FIGURE 4-1 shows the schematic for the synthesis of geopolymer concrete cured

in the oven at 75oC. Compressive strength of three specimen from each batch were

determined at 7 and 28 days using the Universal Testing Machine (UTM) in accordance

to the standard method for determining compressive strength of cylindrical samples

(ASTM, 2010a).

4.2 Sampling and Sample Preparation

Sample preparation is considered one important part of the analytical process for

which the samples are prepared to simulate and meet the requirements of specific test

scenario. Material in the monolith form would be used for service life analysis while

materials in crushed or granular form would be used for end of life analysis. Samples for

end of life investigation are crushed into smaller fragments in a steel mortar shown in

54

FIGURE 4-2. The fragments are then combined and thoroughly homogenized to form a

composite sample.

FIGURE 4-1: Schematics of the geopolymer concrete production

FIGURE 4-2: Steel pestle and mortar used in crushing the geopolymer concrete

55

Representative samples of each geopolymer concrete are obtained using cone and

quartering method (FIGURE 4-3) in accordance with the procedures outlined in ASTM

C702 (ASTM, 2003). In the cone and quartering process, the sample is poured into a heap

to form a radial symmetry which is flattened and divided into four quadrants, opposite

quadrants are combined to form reduced sample and the other quadrant discarded. This

sub sampling process is continued as needed to obtain the needed amount of

representative sample.

FIGURE 4-3: Cone and quartering process (After (Allen, 2003))

FIGURE 4-4: Crushed and size reduced geopolymer concrete sample

56

The representative sample (right image in FIGURE 4-4) is ground into fine

powder using the ring grinder shown in FIGURE 4-5. Test samples required for the

analytical tests are obtained by sieving the representative samples to particle size less

than 150 µm (sieve #100).

FIGURE 4-5: Rocklab ring grinder used in grinding the geopolymer concrete samples

4.3 Summary

This chapter presents the synthesis of different geopolymer concrete mixes and

the preparation of the concrete samples for analysis. The geopolymer concrete created

has consistent workability and w/c ratio of about 0.36. The w/c is the ratio of the water

used in the synthesis to the cementitious solids which include the amount of CFA, SF,

NaOH and Ca(OH)2 in the mix design. As the amount of Ca(OH)2 increases, the

workability of the geopolymer concrete reduces because the material harden faster. At

above 2% Ca(OH)2, the geopolymer concrete harden before placement in the mold which

makes the addition of 2% Ca(OH)2 the optimum amount that can be used in the

geopolymer concrete synthesis in accordance with the procedure used for this study.

57

The use of two curing regime (heat curing at 75oC and curing without heat) aims

to identify the effect heat curing has on the leachability and strength of geopolymer

concrete. The main observation from the synthesis of geopolymer concrete using the two

curing regime is the presence of excessive efflorescence on the surface of the geopolymer

concrete cured without heat (FIGURE 4-6). The heat cured geopolymer concrete samples

does not exhibit any efflorescence. Efflorescence is a white powdery deposit of soluble

salts such as sodium carbonate hydrate, sodium carbonate or sodium phosphate hydrate

on the surface of concrete when the soluble salt migrate to the surface of the concrete and

moisture evaporates leaving behind the salt deposit on the surface which then crystallize

(PCA, 2012). Temuujin et al. (2009) reported that efflorescence is an indication of

insufficient geopolymerization which implies that the heat cured geopolymer concrete

forms greater level of geopolymerization.

FIGURE 4-6: Cured geopolymer concrete a) cured without heat, b) heat cured

a b

CHAPTER 5: CHARACTERIZATION OF THE MATERIALS

Characterization of the starting materials and the produced geopolymer concretes

are discussed in this chapter. All the characterization is completed according to standard

protocols. The properties covered are chemical composition and particle size distribution

of the starting materials, compressive strength of the geopolymer concretes, acid/base

neutralization capacity, moisture content and bulk density of all the materials.

5.1 Chemical Composition by X-Ray Fluorescence (XRF) Analysis

The chemical composition of the CFA and SF presented in TABLE 5-1 was

determined using XRF analysis. The analysis was completed by sending the samples to

the geological sciences department at the Michigan State University, East Lansing,

Michigan.

TABLE 5-1: Chemical composition of the CFA and SF (mass %)

SiO2 Al2O3 CaO Fe2O3 MgO Na2O K2O MnO P2O5 TiO2 LOI*

CFA 54.83 28.24 2.45 4.99 0.90 0.22 2.42 0.90 0.23 1.59 3.81

SF 98.48 0.18 0.17 0.18 0.08 0.00 0.12 0.08 0.01 0.00 0.74

*LOI = Loss on ignition

The CFA contains 88% SiO2+Al2O3+Fe2O3 and 2.5% CaO (low calcium) making

the material to be classified as a class F ash according to the ASTM C618 standard. This

type of ash is widely used in the synthesis of geopolymer although Class C (high

calcium) ash can also be used. The only problem with the use of Class C ash is that it

59

makes the geopolymer set very fast (Tempest, 2010). The SF on the other hand contains

98% SiO2, a high content of reactive silica required for the synthesis of higher order

geopolymer with higher strength. The use of SF as a source of reactive silica is a

deviation from the norm of using sodium silicate (Na2SiO3), this is because we want to

increase the use of waste material in the synthesis of our geopolymer.

5.2 Particle Size Distribution (PSD)

Sieve analysis based on ASTM C136 (ASTM, 2006a) standards was performed

on the CA and FA to determine the particle size distribution (PSD), the result obtained

from this analysis is presented in FIGURE 5-1. The PSD of CA and FA meet the

requirements for the aggregates that would produce concrete that are very easy to place.

For the fine particle sizes, Beckman coulter LS 13 320 laser diffraction particle size

analyzer (FIGURE 5-2) was used to determine the PSD of CFA and SF (FIGURE 5-3

and 5-4). The instrument uses the principle of light scattering to determine the particle

size distribution of sample in powder form.

0

10

20

30

40

50

60

70

80

90

100

0.10 1.00 10.00

Percen

tag

e f

iner b

y w

eig

ht

(%)

Sieve size (mm)

CA FA

FIGURE 5-1: Particle size distribution of the aggregates

60

The principle of light scattering involves analyzing light scattering pattern

(diffraction) produced when particles of different sizes are exposed to a beam of light

(Beckman Coulter, 2011). In the laser instrument, particles of the sample are suspended

in water, diluted to decrease interference, and pass through a cell where laser beam is

directed towards the particles (OEWRI, 2008). The PSD of the CFA and SF was

determined by measuring the pattern of light scattered by the particles in the sample since

each particle has different scattering pattern which is correlated to the particle size

distribution of the sample.

As shown in FIGURES 5-3 and 5-4, the CFA has particle that range in size from

0.04 µm to 309 µm while the SF has particle size in the range of 0.04 µm to 1800 µm.

The two materials have relatively well graded particle size distribution and mean particle

size of 47 µm and 277 µm respectively.

FIGURE 5-2: Laser diffraction particle size analyzer

61

FIGURE 5-3: Particle size distribution of CFA and SF (volume % )

FIGURE 5-4: Particle size distribution of CFA and SF (cumulative volume %)

62

5.3 Compressive Strength of the Geopolymer Concrete

Compressive strength of the geopolymer concretes was determined at 7 and 28

days in accordance to the standard test method for compressive strength of cylindrical

samples. FIGURES 5-5 and 5-6 present the average compressive strength from three

specimens of the geopolymer samples cured at 75oC and ones cured without heat.

For the heat cured geopolymer concrete (FIGURE 5-5), the GPC sample exhibit

the highest strength, with 7 day strength of 47 MPa and 28 days strength of 56 MPa. The

lowest compressive strength was measured in the GP1 sample with 0.5% hydrated lime

content. The 7 days strength is 37 MPa and the 28 days strength is 42 MPa which are

lower than the strengths measured in the GPC specimens that do not contain additional

hydrated lime. When 1.0% hydrated lime was added (GP1), the strength of the concrete

increased slightly to 44 MPa for 7 days and 51 MPa for 28 days. Further addition of lime

up to 2.0% resulted in reduction in the strength of the GP3 geopolymer concrete to 42

MPa at 7 days and 43 MPa at 28 days.

FIGURE 5-5: Compressive strength of the geopolymer concrete cured with heat

0

10

20

30

40

50

60

70

GPC GP1 GP2 GP3

Com

pre

ssiv

e st

rength

(M

Pa)

7 days 28 days

63

The highest compressive strength of the geopolymer concrete cured without heat

(FIGURE 5-6) is less than 20 MPa for all the geopolymer concrete samples. The 7 days

compressive strength of the GPC and GP1 sample are the lowest strength (7 MPa) which

increase gradually by 1 MPa as the hydrated lime content increases from 1.0% and 2.0%

in the GP2 and GP3 samples respectively. At 28 days on the other hand, the GPC

produces the highest compressive strength of 18 MPa which reduces as the amount of

hydrated lime in the geopolymer concrete increases from 0.5% to 1.0% and finally 2.0%

in the GP1, GP2 and GP3 samples. According to Yip et al. (2005), previous studies found

that the addition of calcium should positively impart the compressive strength of

geopolymers, but that same conclusion cannot be made for the geopolymer concretes

produced in this study.

All the geopolymer concretes produced except the 7 days sample cured without

heat shows reduction in the overall compressive strength as the content of hydrated lime

increases from 0% to 2%. In all these samples, there was an observed increased in

compressive strength at 1.0% hydrated lime content when compared with the previous

sample with 0.5% hydrated lime. The most important observation from the result is that

the heat cured geopolymer concrete produced the highest compressive strength and the

average 28 days compressive strength of samples exceeds the design strength of 41 MPa

(6,000 psi).

Kruskal-Wallis test and Tukey-Kramer HSD pairwise comparison test conducted

at 95% confidence level (α = 0.05) are the statistical analysis tools used in this section.

The results from the statistical analysis are presented in appendix C. According to the

Kruskal-Wallis test result shown in appendix C1, the 7 days compressive strength of the

64

geopolymer concrete cured without heat are not significantly different (p-value =

0.0216). The Tukey-Kramer pairwise comparison of the compressive strength showed

that the following pairs have significantly different compressive strength: GP3vs GPC (p-

value = 0.0009), GP3 vs GP1 (p-value = 0.0042) and GP2 vs GPC (p-value = 0.0158). On

the other hand, the 28 day compressive strength of the geopolymer concrete cured

without heat (appendix C2) is not significantly different (p-value = 0.4415), so there is

no need for pairwise comparison.

As shown in appendix C3 and C4, the 7 day compressive strength of the

geopolymer cured with heat did not show any significant difference (p-value = 0.2479)

but the statistical analysis of 28 days strength reveals that there is significant difference

(p-value = 0.0237) between the compressive strength of the geopolymer concrete

samples. The pairwise comparison showed the some pair of the geopolymer concrete

samples: GP2 vs GP1 (p-value = 0.0312) and GPC vs GP3 (p-value= 0.0488) have

compressive strength that are significantly different.

FIGURE 5-6: Compressive strength of geopolymer concrete cured without heat

0

5

10

15

20

25

30

GPC GP1 GP2 GP3

Com

pre

ssiv

e st

rength

(M

Pa)

7 days 28 days

65

5.4 Acid and Base Neutralization Capacity (ANC/BNC)

The quantity of acid or base added to each material to maintain a constant pre-

defined pH value is termed the acid and base neutralization capacity (ANC/BNC) of the

material. The amount of acid and base required to bring the starting materials and

produced geopolymer concretes to pre-defined pH values were determined by completing

the pretest titration outlined in the draft USEPA method 1313 (USEPA, 2009b) and used

to plot the acid/base titration curve of the samples.

The ANC/BNC procedure involves adding samples of the material into eight

containers containing deionized water and acid or base at liquid to solid ratio (L/S) of 10.

pH of the resulting suspension was measured after 24 hours and used to plot the

ANC/BNC curve of the material. FIGURES 5-7 to 5-12 show the ANC/BNC curves of

CFA, SF, GPC, GP1, GP2, and GP3. Information from these figures shows the natural

pH of the materials when acid addition is zero milliequivalent (meq) per gram of the

material. Other information shown is the acid or base addition that will get the material to

the target pH values of 1, 3, 5, 7, 9, 11 and 13 required for the pH dependence extraction.

FIGURE 5-7: ANC/BNC curve of CFA

0

2

4

6

8

10

12

14

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Elu

ate

pH

Acid Addition [meq/g]

Targets Natural pH

66

FIGURE 5-8: ANC/BNC curve of SF

FIGURE 5-9: ANC/BNC curve of GPC

0

2

4

6

8

10

12

14

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Elu

ate

pH


A Targets Natural pH

0

2

4

6

8

10

12

14

-6.0

-5

.5

-5.0

-4

.5

-4.0

-3

.5

-3.0

-2

.5

-2.0

-1

.5

-1.0

-0

.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Elu

ate

pH


28 d heat Targets Natural pH

67

FIGURE 5-10: ANC/BNC curve of GP1


0

2

4

6

8

10

12

14

-6.0

-5.5

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Elu

ate

pH



0

2

4

6

8

10

12

14

-6.0

-5.5

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Elu

ate

pH



68


5.5 Material Natural pH

Natural pH of the materials was determined from the pre titration test conducted

to determine the ANC/BNC as shown in FIGURES 5-7 to 5-12. TABLE 5-2 summarizes

the natural pH of all the materials. According to TABLE 5-2, the CFA and the

geopolymer concrete samples (GPC, GP1, GP2, and GP3) are all alkaline materials while

the SF has a pH that makes it a material with neutral pH.

TABLE 5-2: Natural pH of the materials

Material Natural pH

CFA 8.67

SF 7.62

GPC 11.60

GP1 11.00

GP2 11.10

GP3 11.20

0

2

4

6

8

10

12

14

-6.0

-5.5

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Elu

ate

pH



69

5.6 Moisture Content and Bulk Density

As-received moisture content of the materials was determined by drying the

samples at 105oC for 24 hours. As shown in TABLE 5-3, most of the materials have

moisture content greater than 1%, only the SF has moisture content of less than 1%. Bulk

density of loose dry fly ash is reported to be about 1,000 kg/m3(Sear, 2001) but the CFA

has a bulk density of about 900 kg/m3. The bulk density of the monolithic geopolymer

concretes were determined to be 2300 kg/m3.

TABLE 5-3: Moisture content and bulk density of the materials

Material Moisture content (%) Bulk density (kg/m3)

CFA 1.8 897.8

SF 0.5 378.4

GPC 1.4 2300.0

GP1 1.7 2300.0

GP2 1.9 2300.0

GP3 1.9 2300.0

5.7 Summary

The geopolymer concretes are alkaline material with pH > 11 and bulk density of

2300 kg/m3. This bulk density is equivalent to the density of normal weight concrete. The

average 28 days compressive strength of the heat cured geopolymer range from 42 MPa

(6013 psi) to 56 MPa (8117 psi) while the average 7 days compressive strength is 37 MPa

(5367 psi) to 47 MPa (6817 psi). In terms of 28 days compressive strength, the heat cured

geopolymer concrete is similar in strength to high strength concrete with compressive

strength of about 40 MPa (6,000psi) (Mehta and Monteiro, 2006). On the other hand,

70

geopolymer concretes cured without heat have average 28 days compressive strength that

ranges from 13 MPa (1937 psi) to 18 MPa (2647 psi) and an average 7 days compressive

strength that ranges from 7 MPa (1015 psi) to 9 MPa (1305 psi). It is obvious from the

results that heat curing is a requirement for the production of geopolymer concrete with

acceptable compressive strength for structural uses. Hydrated lime did not positively

impact the compressive strength of the geopolymer concretes, it result in the reduction in

strength of geopolymer concrete as the lime content increases but exhibit high strength at

the optimal lime addition of 1%.

Due to the presence of efflorescence on the surface of the geopolymer concretes

cured without heat and their low compressive strength, the material was not considered

for further investigation since it would only be suitable for low strength structural

applications like walkway, curbs and road divider. The heat cured geopolymer concretes

on the other hand are considered for further investigation because they meet the basic

strength requirement (40 MPa or 6000 psi) for concrete used in high strength structural

applications.

CHAPTER 6: LABORATORY LEACHING TEST METHODS

6.1 Introduction

The leaching test methods designed to evaluate leaching of elements from

cementitious material such as geopolymer concrete samples during their service life (in

monolith form) and at the end of service life (in granular form) are presented in TABLE

6-1. Batch leaching test such as the pH dependence test, water leach test and Dutch

availability test are considered for granular state of the samples while the tank test is used

for monolithic state of the samples. After completion of the leaching test, the samples

were filtered and the filtrate (leachate) for cation analysis was acidified to pH < 2 using

50% HNO3 in order to minimize metal precipitation and adsorption onto the sample

containers prior to using the inductively coupled plasma atomic emission spectroscopy

(ICP-AES). Ion chromatography (IC) was used for anion analysis of water leached

samples and the leachates were not acidified.

According to the preliminary investigation presented in Section 3.6.1, elements

such as As, Cr, Se, V and Mo that form oxyanion leach out more in the high pH condition

similar to the alkaline state that would exist in the pore solution of geopolymer concretes.

Although the concentration of other elements in the leachates is measured, this chapter

would focus mainly on the leaching of As, Cr and Se since they are considered elements

with more environmental concerns due to their mobility and toxicity at the different

oxidation states.

72

TABLE 6-1: Relevant leaching test during life cycle of cementitious materials

Material Life cycle period condition Area of use Relevant leaching

test

Cementitious

materials

Service life Monolith Foundation,

Façade,

containers,

sewer pipes

Tank test

End of service

life

(after demolition)

Granular

and reduced

fragments

Disposal,

aggregates in

concrete and

road

construction

pH dependence

test

Availability test &

Column test

Source: Van der Sloot and Kosson (2003)

6.2 pH Dependence Leaching Test

The pH dependence test is conducted to determine mobility of elements from the

geopolymer concrete samples when they are exposed to different pH condition. The test

was based on the USEPA draft method 1313 (USEPA, 2009b). In this test, deionized

water was added to granular/powdered geopolymer concrete samples in nine plastic

bottles at L/S ratio of 10. HNO3 or NaOH was used to maintain the pH to pre-selected pH

values of 3, 5, 7, 9, 11 and 13. The amount of HNO3 or NaOH required to make the

material reach the selected pH values was obtained from the pre titration curve presented

in FIGURES 5-7 to 5-12. FIGURE 6-1 shows the experimental setup for the pH

dependence test. Three method blanks without the samples are added to the pH extraction

in order to identify any contaminations that might be introduced by the deionized water,

HNO3 or NaOH. The analyses were carried out in duplicates, stopped after 24 hours and

the leachates filtered, then acidified before storing at 4oC.

73

FIGURE 6-1: pH dependence test experimental setup

The concentrations (mg/l) of elements measured in the leachates using the ICP-

AES were used to calculate the amount of the element leached (mg/kg) from each

material. In cases where the measured concentration is less than the detection limit (DL)

of the instrument, the concentration value DL/2 was used in the calculation of the amount

leached. The average (n=2) result of the pH dependence mobility of As, Cr and Se from

the CFA, SF, GPC, GP1, GP2 and GP3 expressed in mg/kg are presented in FIGURES 6-

2 to 6-7 while FIGURES D-1 to D-6 in appendix D show the pH dependence mobility of

the other elements. As shown in FIGURES 6-2 to 6-4, the mobility of the three elements

(As, Cr and Se) is highest at pH 1 but reduces as the pH increases. As mobility from CFA

reached 32 mg/kg at pH 1 and reduces to 1 mg/kg at pH 4 and pH 11. The amount

leached increases slightly at pH 7 to 4 mg/kg. The highest mobility in the alkaline pH is 7

mg/kg while 32 mg/kg is the highest at the acidic pH range. Mobility of As from the SF

74

is constant at 8 mg/kg irrespective of the pH although it was difficult filtering the

leachates obtained from the extractions between pH 4 and 11.

FIGURE 6-2: pH dependence mobility of As from the CFA and SF

The amount of Cr leached from both the CFA and SF is lower than the amount of

As leached (FIGURE 6-3). The highest amount of Cr released (18 mg/kg) from CFA

occurs at pH 1 while the highest amount released (4 mg/kg) in the alkaline pH occurs at

pH 13. On the other hand, the amount of Cr released from the SF is less than 1 mg/kg as

shown in FIGURE 6-3.

75

FIGURE 6-3: pH dependence mobility of Cr leached from the CFA and SF

Highest mobility of Se (11.8 mg/kg) occurs in the acidic pH which reduces to the

lowest mobility of 1.5 mg/kg at pH 4. At the neutral pH, the amount of the element

released increases slightly to 8 mg/kg and then starts to drop to another low mobility of 3

mg/kg at pH 11. After this point, the mobility of Se increases to another high value of 8.5

mg/kg at pH 13. The mobility of Se from the SF is constant at 6 mg/kg from pH 1 to 11,

but drops to the lowest amount of 5 mg/kg at pH 13. Presented in FIGURES D-1, D-2,

and D-3 in appendix D, the mobility of Al, Ca, Fe, Mg, B, Ba, Cu, Mn, V and Zn from

CFA is highest in the acidic pH. Na, Mo and Si have the highest mobility from the CFA

occurring in the alkaline pH.

76

FIGURE 6-4: pH dependence mobility of Se from the CFA and SF

Elements that include Al, Si, Ca, V, Mo and Fe have constant mobility across the

pH range (FIGURES D-1, D-2, and D-3 in appendix D). Others like Na and B exhibit

higher mobility in the alkaline pH while the remaining elements (Mg, Ba, Cu, Mn, and

Zn) displays higher mobility in the acidic pH.

Different pattern of element release were observed from the geopolymer concrete

samples as shown in FIGURES 6-5 to 6-7 and FIGURES D-4 to D-6 (in appendix D). In

all the geopolymer concrete samples, the leaching of As starting with high value at low

pH reduces with increasing pH and reached the lowest value in the pH range of 3 - 7

(FIGURE 6-5). The highest amount leached occurs in the alkaline pH of 13. In the

alkaline pH, among all the geopolymer samples, GP2 exhibits the lowest mobility of As

while GP3 displays the lowest at pH 1.

77

FIGURE 6-5: pH dependence mobility of As from the geopolymer concretes

The mobility of Cr from the geopolymer concrete samples shown in FIGURE 6-6

reveals that the element leach out more at pH 1 but drops rapidly at pH between 3 and 4

depending on the geopolymer concrete sample. The lowest mobility of this element

occurs in the alkaline pH range. GP2 samples has the minimum amount of the Cr leached

in the acidic pH but the mobility from the other materials becomes the same from pH 5

(FIGURE 6-6). The concentration of the Cr measured in the leachates from the

geopolymer concretes at pH 5 to pH 13 is less than the detection limit (DL) of the

instrument.

78

FIGURE 6-6: pH dependence mobility of Cr from the geopolymer concretes

Mobility of Se from the geopolymer concretes presented in FIGURE 6-7 reveals

that in most of the samples, the element leach out more in the alkaline pH. The lowest

amount of Se was leached at pH between 3 and 6 with an amount 1.5 mg/kg after that its

starts to increase as the pH increases until it reached the highest mobility at pH 13. GP2

samples display constant mobility throughout the pH range mainly because the

concentration measured in the leachates is less than the DL and the value DL/2 was used

to calculate the amount leached from the material. It can be seen from the results

presented in FIGURES 6-5 to 6-7 that the mobility of the elements is reduced in the GP2

geopolymer concretes which has 1.0% hydrated lime added during the synthesis.

Mobility of two other oxyanion forming elements (Mo and V) presented in FIGURE D-4

79

in appendix D shows that these elements have the lowest mobility from the GP2 concrete

samples.

FIGURE 6-7: pH dependence mobility of Se from the geopolymer concretes

Different leaching pattern was observed for the other elements as shown in

appendix D (FIGURES D-5 and D-6). All the elements except Si and Na display higher

mobility in the acidic pH. The mobility of Na and Si is highest in the alkaline pH.

Elements such as Al, Si, Na, Fe, Mg and Ca have very high mobility from the

geopolymer concretes while the mobility of elements like B, Ba, Cu, Mn and Zn are

moderate. In all, mobility from the GP2 sample is still the lowest. This suggests that GP2

geopolymer concrete was able to help reduce the mobility of majority of the elements that

80

are released from the geopolymer concrete, and may provide an indication of the range of

the optimum Ca content required to immobilize majority of the element.

6.3 Dutch Availability Test

The samples was subjected to the Dutch availability test to determine the

maximum amount of each element leachable from the starting material and geopolymer

samples under the worst-case environmental condition (EA, 2005a). The test is

performed at room temperature on size reduced sample (<150 µm) in order to ensure

complete dissolution of the constituents (Cappuyns and Swennen, 2008). The test method

consists of two extraction steps in which the pH was maintained at 7 and 4 using HNO3.

The extraction at pH 7 is conducted to simulate the leaching of oxyanion forming

elements and at pH 4 as the most extreme natural pH condition for cationic elements‘

mobility (Fällman, 1997).

This test method for which schematic is presented in FIGURE 6-8, 8 g of dry

sample was weighed into an acid washed beaker, and deionized water added at a liquid to

solid (L/S) ratio of 50. The suspension was agitated using magnetic stirrer while the pH

continuously controlled to pH 7 ± 0.5 using 2M HNO3 for 3 hours after which the

mixture was filtered through a 0.45µm membrane filter. The residue from the filtration

process was used for the second extraction step and the pH controlled to pH 4 ± 0.5 for

additional 3 hours. The liquid obtained after the filtration was combined with the liquid

from the first extraction step and acidified to pH < 2 using 50% V/V HNO3.

Concentrations of As, Cr and Se in the leachates are measured using the ICP-AES and

were used to calculate the average (n=3) availability of each element from the materials

expressed in mg/kg of the tested material.

81

FIGURE 6-8: Schematics of the Dutch availability test

FIGURE 6-9 shows the amount of the elements leached from the CFA and SF

while FIGURE 6-10 contains result for the geopolymer concrete samples. It can be seen

from these results that As and Se are the two elements that leach considerably from all

the materials. The amount of Cr leached is however very small in all the materials tested.

FIGURE 6-9: Availability of As, Se and Cr from the starting materials

0

2

4

6

8

10

12

14

16

CFA SF

Am

ou

nt

leach

ed (

mg/k

g)

Starting materials

Arsenic (As) Selenium (Se) Chromium (Cr)

Residue Dry material

1st step

L/S: 50

pH: 7

Time: 3 hrs

2nd

step

L/S: 50

pH: 4

Time: 3 hrs

Filtration Filtration

Combined

leachates

82

According to the availability test result presented in FIGURE 6-9, the mobility of

As from CFA reached 13 mg/kg whereas the mobility of Se is about 12.9 mg/kg and Cr is

around 4 mg/kg. The SF on the hand indicates more leaching of Se than As and Cr. The

amount of Se leached in the SF is 8 mg/kg while the amount of As and Cr released from

the material are respectively 7 mg/kg and 0.5 mg/kg. It can be seen from the result that

As and Se are readily available for leaching in the starting materials.

FIGURE 6-10: Availability of As, Cr and Se from geopolymer concrete samples

Mobility of As is highest in all the geopolymer concrete samples (see FIGURE 6-

10) with the maximum amount leached close to 10 mg/kg. In the case of Cr, its mobility

from the geopolymer concrete is very small which signifies that the material is not readily

leachable. One very important observation from the results shown in FIGURE 6-10 is

that the GP2 geopolymer concrete have lower amount of leached elements. There was a

10.5% reduction in the amount of As leached from the GP1 to GP2 sample and from GP2

0

2

4

6

8

10

12

GPC GP1 GP2 GP3

Am

ou

nt

lea

ched

(m

g/k

g)

Geopolymer concrete

Arsenic (As) Selenium (Se) Chromium (Cr)

83

to GP3 sample the mobility of As later increased by 11.7%. The reduction of Se from the

GP1 to GP2 sample was 25% and from GP2 to GP3, there was a 10% increase in the

mobility. Cr on the other hand, shows almost constant mobility from the geopolymer

concrete samples. The result suggests that the GP2 geopolymer concrete with 1.0%

additional hydrated lime lead to considerable reduction in the amount of As and Se

released from the geopolymer concrete.

6.4 Tank Test

Tank test based on the USEPA draft method 1315 (USEPA, 2009c) was used to

determine element mobility from the monolithic fly ash based geopolymer concrete. The

test is designed to provide the release rates of the constituent elements in the monolithic

geopolymer concrete. In this test, monolithic cylinder sample of the geopolymer

concretes was completely submerged or immersed in a given volume of deionized water

(FIGURE 6-11 and 6-12) and kept in static condition at ambient temperature. Amount of

deionized water added during the test was based on a liquid to solid exposed surface area

(L/Sa) ratio of 7±1. The deionized water was replenished with fresh deionized water at

nine intervals: 0.08 day, 1 day, 2 days, 7 days, 14 days, 28 days, 42 days, 49 days and 64

days and the weight of the monolith geopolymer determined after each leaching interval

in order to measure the amount of water absorbed into the solid matrix at the end of each

interval (USEPA, 2009c). The collected leachates were filtered through a 0.45µm

membrane filter and later acidified to pH < 2 using HNO3. Concentration of As, Cr and

Se measured in the leachates were used to determined the average (n=2) amount of the

elements released from the monolithic geopolymer concrete samples.

84

FIGURE 6-11: Schematic of the tank leaching test

FIGURE 6-12: the tank leaching test setup

The release of As, Cr and Se over the leaching duration from the geopolymer

concrete is presented in FIGURES 6-13 to 6-15. Each figure shows the cumulative

Lid

HDPE

Bucket

DI water

Stand

85

amount of each element released (mg/m2) and the release flux (mg/m

2.s) across the

exposed surface of the geopolymer concrete. The cumulative release plot and flux plot

were used to determine the mechanism responsible for the leaching.

FIGURE 6-13: Release of As from the geopolymer concrete samples

As shown in FIGURE 6-13, the cumulative amount of As released from the

geopolymer concretes reached 300 mg/m2

and the plot can be divided into three regions

86

which depict the leaching mechanism of the element. From the beginning of the test to 1

day, surface wash-off is the controlling mechanism. This mechanism is due to initial

wash-off of soluble material on the outside of the monolith concrete. EA (2005b)

reported that the slope of the region is less than or equal to 0.35. Between 1 day and 9

days of leaching, diffusion controlled mobility is the dominant leaching mechanism. This

is the normal mechanism responsible for leaching from monolithic materials and the

slope of the cumulative release plot is 0.5 ± 0.15 (EA, 2005b). After 9 days of leaching,

the dominant mechanism changes to depletion which is associated with reduction in

amount of the element released. In the surface wash-off region of the plot, As mobility

from the GPC sample is the highest while the lowest mobility occurs in the GP3 sample

(FIGURE 6-13) but at the region where depletion dominates, the GP2 sample has the

lowest mobility of As (FIGURE E-1 in appendix E).

The cumulative release plot of Se shown in FIGURE 6-14 reveals that the element

exhibits the same leaching behavior as As. The leaching mechanism is also divided into

surface wash-off, diffusion and depletion. The maximum amount of Se leached in this

case reaches 130 mg/m2. During the initial stage of the leaching, the GP1 and GP3

samples exhibits the lowest release of Se but in the depletion region of the plot, mobility

of Se from the GP2 sample is the lowest (FIGURE E-2 in appendix E).

87

FIGURE 6-14: Release of Se from the geopolymer concrete samples

From FIGURES 6-13 and 6-14, it is obvious that the cumulative release of As and

Se tend to a flat plateau towards the end of the leaching duration and the flux tend to zero

with the value dropping rapidly towards the end of the leaching. This leads to depletion

of the element as the leaching progresses. Cr on the other hand, exhibits an ever

increasing cumulative release as shown in FIGURE 6-15. The element does not display

similar leaching behavior to the previous two elements; there is still more of the element

88

available for leaching at the end of the leaching duration. The entire geopolymer concrete

sample display the same pattern of Cr release that reached a maximum value of 3 mg/m2.

The release mechanism in this case is a combination of surface wash-off, diffusion and

dissolution.

FIGURE 6-15: Release of Cr from the geopolymer concrete samples

89

The cumulative release plots showed that As has the highest mobility from the

geopolymer concretes and that the mobility of As and Se attains a plateau which indicates

reduction in elements availability (depletion of the elements). Cr mobility on the other

hand continues to increase over the leaching duration.

6.4.1 Leachability Index (LX) of the Elements

To further understand the mobility of these elements from the geopolymer

concretes, the fickian diffusion model based on fick‘s second law of diffusion was

employed to determine the leachability index (LX) of the elements (Kosson et al., 2002;

Dermatas et al., 2004), which would give the relative mobility of the elements. An

analytical solution (Equation 6.1) of the fickian diffusion model which assume zero

concentration at the solid-liquid interface (Kosson et al., 2002) was used to calculate the

effective diffusion coefficient (De) for each leaching interval using the relationship in

Equation 6.2.

(6.1)

(6.2)

Where is the effective diffusion coefficient for each element (m2/s), M is the

cumulative amount of element leached (mg/m2), ρ is the bulk density of the monolithic

geopolymer concrete (kg/m3), is the maximum leachable amount of each element

determined from the availability test (mg/kg), is the cumulative time at the end of the

current leaching interval i (s) and is the cumulative time at the end of the previous

leaching interval i-1 (s).

90

The LX defined mathematically using Equation 6.3 (Pariatamby et al., 2006) was

determined from the negative logarithms of the mean effective diffusion coefficient

calculated from Equation 6.2. The LX values are presented in TABLE 6-2.

(6.3)

Where n is the number of particular leaching period, m is the total number of individual

leaching periods, β is a constant (1.0 m2/s) and Di is the effective diffusion coefficient of

constituent i (m2/s).

TABLE 6-2: Leachability index (LX) of As, Se and Cr from geopolymer concrete

LX value

As Se Cr

GPC 10.6 10.7 11.4

GP1 10.5 10.5 11.4

GP2 10.4 10.3 11.4

GP3 10.5 10.5 11.5

According to Dermatas et al. (2004) and EA (2005b), the relative mobility of the

elements or any other contaminants is evaluated using the LX value which varies from 5

(very mobile) to 15 (immobile). TABLE 6-3 contains information used to interpret the

LX value. The lower the LX value the higher mobility of the element. The LX value

shown in TABLE 6-2 reveals that As and Se have high mobility from the geopolymer

concrete samples while Cr has average mobility from the same geopolymer concrete

91

samples. The LX value can therefore be used in making decision on utilization of the

geopolymer concrete. Dermatas et al. (2004) reported that any material that has elements

or contaminant LX value less than 8 is not suitable for disposal or utilization in

applications such walkways.

TABLE 6-3 :The LX range for different rate of mobility

Low mobility LX >12.5

Average mobility 11.0 < LX < 12.5

High mobility LX < 11.0

Source: EA (2005b)

6.4.2 Depletion of the Elements in Relation to Availability

The amount of each element leached per unit mass in the tank test over the 64

days leaching duration was estimated in order to determine the depletion of the element

in relation to the availability as obtained from the Dutch availability test. The amount

leached per unit mass in the tank test (U tank) is calculated using equation 6.4.

(6.4)

Where U tank is the amount of each component leached in the tank test (mg/kg), C64 is

the cumulative amount of the element leached after 64 days (mg/m2), A is the surface

area of the sample (m2), and m is the mass of the sample (kg).

FIGURES 6-16 to 6-18 shows the comparison of the amount of As, Se and Cr

leached from the monolith geopolymer concrete in relation to the amount leached using

the availability test. As shown in FIGURE 6-16, for the GP1 and GP2 samples, the

estimated amount of As leached in the tank test exceeds the amount leached in the

availability test.

92

FIGURE 6-16: As availability in tank test in relation to total availability

FIGURE 6-17: Se availability in tank test in relation to total availability

7.5

8.0

8.5

9.0

9.5

10.0

GPC GP1 GP2 GP3

Am

ou

nt

leach

ed (

mg/k

g)

Geopolymer concrete

U avail U tank

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

GPC GP1 GP2 GP3

Am

ou

nt

leach

ed (

mg/k

g)

Geopolymer concrete

U avail U tank

93

The amount of Se estimated in the tank test for GP2 exceeds the amount leached

in the availability test (FIGURE 6-17). In the case of Cr, the estimated amount is much

lower than the amount leached in the availability test (FIGURE 6-18). These results were

used to determine the extent of depletion of the each element. As presented in TABLE 6-

4, the extent of depletion is presented as the percentage depletion of each element in

relation to the availability. The percentage depletion of As and Se is very high, while Cr

have low depletion. The greater than 100 % result suggests that at the end of the 64 days

leaching duration, all of the As in GP1 and GP2 and all the Se in GP2 that are available

for leaching have been released. On the other hand, result with value less than 100%

suggests that there is still some amount of the element that can be leached from the

sample.

FIGURE 6-18: Cr availability in tank test in relation to total availability

0.00

0.05

0.10

0.15

0.20

0.25

0.30

GPC GP1 GP2 GP3

Am

ou

nt

leach

ed (

mg/k

g)

Geopolymer concrete

U avail U tank

94

TABLE 6-4: Percentage depletion in relation to total available fraction

Percentage after 64 days (%)

As Se Cr

GPC 92 82 26

GP1 102 92 29

GP2 107 121 27

GP3 99 94 26

6.5 Water Leach Test

The water leach test (WLT) was used to obtain aqueous solution of the

concentration of dissolved elements used for the geochemical speciation modeling.

Standard procedure described in ASTM D3987(ASTM, 2006c) was used. In this test

method, 200 ml of deionized water was added to 10 g of the granular geopolymer

concrete sample at L/S ratio of 20. The mixture was agitated for 18 hours and allowed to

settle for 15 minutes before filtering through a 0.45µm membrane filter. The ICP-AES

and IC were used to respectively measure the concentration of cations and anions in the

leachates. TABLE 6-5 shows the measured average (n=2) pH and temperature of the

leachates, while TABLES 6-6 and 6-7 contains average (n=2) concentration of cations

and anions measured in the leachates. This information is used as inputs into the

geochemical modeling program.

TABLE 6-5: Temp and pH of the water leach test leachates

GPC GP1 GP2 GP3

pH 11.23 11.26 11.51 11.14

Temperature [C] 25 25 25 25

95

TABLE 6-6: concentration of cations in the water leach test leachates

Elements

Concentration (mg/l)

GPC GP1 GP2 GP3

Al 0.45 1.26 0.75 0.69

As 1.02 1.02 1.02 0.93

Ba 0.03 0.03 0.03 0.03

B 1.78 1.79 1.78 1.65

Ca 0.64 1.05 0.78 1.13

Cr 0.03 0.03 0.03 0.03

Cu 0.03 0.03 0.03 0.03

Fe 0.33 0.63 0.47 0.42

Mg 0.16 0.26 0.22 0.19

Mn 0.03 0.03 0.03 0.03

Mo 0.27 0.26 0.26 0.24

Se 0.41 0.42 0.42 0.37

Si 160.00 169.50 183.00 153.00

Na 564.50 556.00 550.00 555.00

V 1.69 1.93 2.11 2.08

Zn 0.03 0.03 0.03 0.03

96

TABLE 6-7: Concentration of anions in the water leach test leachate

Elements

Concentration (mg/l)

GPC GP1 GP2 GP3

Br- 0.05 0.05 0.05 0.05

Cl- 1.20 1.30 1.95 9.70

F- 0.40 0.40 0.37 0.35

NO3- 0.20 0.11 0.11 0.20

PO43-

31.50 32.50 33.00 16.00

SO42-

155.00 150.00 150.00 145.00

As shown in TABLE 6-5, the pH of the material is greater than 11 which is a

confirmation of the material pH result presented in section 5.5. As shown in FIGURE 6-

5, concentrations of As, Se, B and Mo are lowest in the GP3 concrete. Higher

concentration of Al, Ca, V and Mg were measured in the leachates as the amount of

hydrated lime in the geopolymer concretes increases. The high amount of NaOH added

during the geopolymer synthesis results in the very high concentration of Na and Si

measured in the leachates. Elements such as Ba, Cr, Mn, Zn and Cu have constant

concentration in all the geopolymer concrete samples mainly because their measured

concentrations in less than the DL of the ICP-AES.

The anion concentrations measured in the leachates (TABLE 6-7) reveal that the

concentrations of SO42-

and PO43-

are high in all geopolymer concrete products with GP3

exhibiting slightly lower values. Concentration of F- measured in the leachates are

equivalent in all geopolymer with GP2 and GP3 samples containing slightly lower values

while Cl-

exhibits an increasing concentration as the amount of added hydrated lime

97

increases in the geopolymer concrete samples. Br- concentration measured in the

leachates is less than the DL of the instrument.

6.6 Risk Associated with Release of the Oxyanion Elements

To assess the potential risk associated with the release of elements from

geopolymer concrete especially the oxyanion forming elements (As, Cr, Se), TCLP

regulatory limit (TABLE 6-8) was used to estimate the maximum allowable amount of

each element that could be released from geopolymer concrete which was then compared

with the actual amount of the elements released from the geopolymer concrete as shown

in TABLE 6-9. The amount of the oxyanion elements (As, Cr, Se) released from the

geopolymer concrete was calculated using results obtained from the WLT conducted

using leaching solution at neutral pH (Section 6.5). Although the TCLP test is usually

performed using acidic leaching solution, it was still used to estimate the leaching of the

oxyanion forming elements from the alkaline geopolymer concrete because TCLP has

maximum allowable concentration that can be used to classify material and waste as a

characteristics hazardous waste. One limitation of estimating the release of oxyanion

elements (As, Cr, Se) using the TCLP regulatory limits is that the actual amount released

might be higher than the reported values.

TABLE 6-8: TCLP Regulatory limits of As, Cr and Se

Elements Concentration (mg/l)

As 5.0

Cr 5.0

Se 1.0

98

TABLE 6-9: Comparison of amount leached from geopolymer (mg/kg)

TCLP

Geopolymer

As Cr Se

As Cr Se

GPC 50.68 50.68 10.14

10.37 0.25 4.11

GP1 50.68 50.68 10.14

10.33 0.25 4.24

GP2 50.68 50.68 10.14

10.29 0.25 4.28

GP3 50.68 50.68 10.14

9.37 0.25 3.79

From the result, the amount of As released from the geopolymer concretes is

about 20% of the released amount based on the maximum allowable concentration for the

TCLP. The amount of Cr and Se released from the geopolymer concrete is also less than

the regulatory amount based on the TCLP test.

The risk associated with the oxyanion forming elements (As, Cr, Se) was assessed

using the USEPA risk based screening levels which considered only human health risks

(USEPA, 2012). Health risks considered are inhalation of particles, incidental ingestion

and dermal contact. The assessment was based on residential risk screening level and

performed using the risk-based screening level calculator which utilized the combination

of exposure assumptions with chemical toxicity values to determine the risk associated

levels. TABLE 6-10 shows the calculated residential risk based screening levels for the

human health risk considered.

99

TABLE 6-10: Residential risk based screening levels

Elements Concentration (mg/kg)

Ingestion Dermal Inhalation

As 2.35E+01 2.79E+02 2.13E+04

Cr NA NA NA

Se 3.91E+02 NA 2.84E+07

NA – None available

Based on the information in TABLE 6-10, all the amount of oxyanion elements

released from the geopolymer concretes are lower than the human risk based screening

levels. This suggests that the human health risk associated with the use of geopolymer

concrete is minimal.

6.7 Summary

The pH dependence test is a powerful laboratory tool for the environmental

assessment of any material. The test on geopolymer concrete reveals that the oxyanion

forming elements As and Se are released more in the alkaline pH. In general, the leaching

trend for the elements is similar in all the geopolymer concrete samples. Most of the

geopolymer concrete displays similar leaching pattern for As and Se and the GP2 sample

exhibit the lowest mobility of As and Se in the alkaline pH. Mobility of Cr from the

geopolymer concretes is however different, with highest mobility at pH 1 that reduces to

negligible amount after pH 4 or 5.

As and Se are elements that are available for leaching from the materials

according to the Dutch availability test. The mobility of these two elements from the GP2

sample is the lowest. The tank test showed that As and Se have high mobility from the

100

geopolymer concretes and that the amount of these element leached from the material

approaches a constant value as the leaching duration increases which means that the

element are being depleted from the geopolymer concretes. Cr on the other hand has

moderate mobility from the geopolymer concretes. The total amount of Cr released from

the geopolymer is relatively small but the cumulative amount released from the

geopolymer concretes is increasing as the leaching process progresses. After 64 days of

leaching As and Se depletion from GP2 exceeds 100% which means that all the element

have leached out. Cr on the other hand has low depletion suggesting that there is still

some amount of the element available for leaching.

The release of the oxyanion forming elements (As, Cr, Se) from the geopolymer

concrete is lower than the estimated release of the elements based on maximum allowable

values from the TCLP regulatory limits. Limited risk based assessment performed on the

geopolymer concretes indicate that the human health risk (incidental ingestion, dermal

contact and inhalation of particles) associated with the material is minimal.

CHAPTER 7: MINERALOGICAL AND MICROSTRUCTURAL

CHARACTERIZATION

7.1 Mineralogical and Microstructural Analysis

The mineralogy and microstructure of the crushed, pulverized geopolymer

samples and the starting materials was determined using X-ray diffraction (XRD) and

scanning electron microscope (SEM).

7.2 X-Ray Diffraction (XRD) Analysis

XRD analysis on the samples aims to confirm the formation of mineral phases

that might be responsible for adsorbing the oxyanion forming trace elements.

PANalytical X‘pert PRO model PW 3040 equipped with θ-θ goniometer and Cu X-ray

tube operated at 45 KV and 40 mA that generates Kα radiation with a wavelength of

1.54Å was used. In this analysis, the sample is front loaded into a zero background

sample holder and mounted on the instrument‘s stage. X-rays beams from the x-ray

source were irradiated on the sample and the interaction of the x-ray with the sample

creates diffracted x-ray beams whose intensity is recorded by the detector (FIGURE 7-1).

Diffractogram are produced by collecting data in the 2θ angle range of 4o to 80

o with a

step size of 0.05o. The measured peak positions and relative intensity of the diffraction

beams are used to determine the crystalline mineral phases present in the samples by

comparing the peak positions (2θ) and intensities from the diffractogram to reference data

102

found in the American Mineralogist Crystal Structure Database (AMSCD). XPowder1, a

free phase identification software was used for the phase identification.

FIGURE 7-1: Schematic of the XRD setup

FIGURES 7-2 to 7-6 show the XRD diffractogram of the starting materials (CFA

and SF) and the geopolymer concretes (GPC, GP1, GP2, and GP3). The diffractogram of

CFA shown in FIGURE 7-2 did not indicate the presence of many crystalline phases,

most likely because there are no sufficient peaks to identify the presence of the phases.

There is a diffuse halo peak at 2θ from 15o to about 35

o which suggest the presence of

amorphous content. The two crystalline phases identified in the fly ash sample are quartz

(SiO2) and mullite (2Al2O3 SiO2). These two mineral phases are among the principal

minerals found in coal fly ash (Rattanasak and Chindaprasirt, 2009). Mineral phases such

as hematite (Fe2O3), and magnetite (Fe3O4) are other mineral phases present in coal fly

ash. There was no observed crystalline phases in the silica fume (FIGURE 7-2), there

was however a halo peak located between 2θ angle of between 15o and 30

o which

indicate the presence of glassy or amorphous content.

1 XPowder is a software for powder X-ray diffraction analysis

103

FIGURE 7-2: XRD diffractogram for the CFA and SF used

FIGURE 7-3 shows the diffractogram of the geopolymer concrete with 0%

hydrated lime (GPC), some of the crystalline phases present in the material cannot be

fully characterized due to peaks with unmatched mineral phases. Minerals that were

successfully identified are quartz, riebeckite, and gypsum as shown in the figure. The

sample also exhibits a not too noticeable hump at 2θ angle of between 25o-30

o that is

associated with the amorphous content of geopolymer. Quartz (SiO2) is the major

crystalline phase in the GPC sample which is attributed to the fact that the material

contains silica sand used in the production of the geopolymer concrete. The other

minerals found in the geopolymer concrete sample are riebeckite

(Na2(Fe,Mg)3Fe2Si8O22(OH)2 - Sodium Iron Magnesium Silicate) and gypsum (CaSO4).

Riebeckite is a sodium rich silicate mineral formed in a highly alkali environment, whose

104

presence in geopolymer mineralogy has not been reported in any literature on the

mineralogy of geopolymer. According to Miyano and Klein (1983), riebeckite is formed

by reaction of iron oxides and quartz in the presence of water. The presence of a lot of

sodium ion, quartz and iron oxides might have actually resulted in the production of

riebeckite instead of calcium containing mineral phases. Occurrence of gypsum in the

sample might be as a result of the absence of ettringite since gypsum is required for the

formation of ettringite or monosulfoaluminate hydrate (Zheng et al., 2011).

FIGURE 7-4 shows the diffractogram of the GP1 sample which contains 0.5%

hydrated lime. According to the information in the figure, the addition of 0.5% hydrated

lime to the geopolymer system led to the formation of new mineral phases. In addition to

quartz, minerals identified in GP1 include bearsite (Be2(AsO4)(OH).4H2O), beraunite

(Fe2+

Fe3+

5(OH)5(PO4)4·4H2O) and lime (CaO).

FIGURE 7-3: XRD diffractogram for the GPC geopolymer concrete

105

FIGURE 7-4: XRD diffractogram for the GP1 geopolymer concrete

The riebeckite that was found in the GPC has disappeared or is converted to

another mineral, most likely beraunite which is a hydrated iron phosphate hydroxide.

Other obvious difference between the GPC and GP1 is the presence of lime and bearsite,

an arsenic containing mineral phase. The XRD pattern in FIGURE 7-5 shows the mineral

phases present in the GP2 sample that contains 1.0% hydrated lime. These diffractogram

reveals the presence of quartz (SiO2), heinrichite (Ba(UO2)2(AsO4)2•11H2O), magnetite

(Fe3O4), downeyite (SeO2), guyanaite (CrO(OH) and cadmoselite (CdSe). There seems to

be stronger quartz peak and some unmatch peaks. In GP2, there is disappearance of the

riebeckite formed in GPC and formation of the bearsite that occurs in GP1. Heinrichite,

an asernic containing mineral phase was also found in this sample.

106


Although the mineral downeyite was identified in this geopolymer sample, the

presence of the mineral is doubted because this mineral is reported to be hygroscopic and

unstable under normal atmospheric conditions (Finkelman and Mrose, 1977). Only two

mineral phases can be successfully identified in GP3 as shown in FIGURE 7-6. These

two minerals are quartz and beraunite which are the minerals that can be found in the

other geopolymer concrete samples. TABLE 7-1 summarizes the mineral phases

identified in all the geopolymer concretes. Only quartz is common to all the geopolymer

concrete and beraunite was identified in only the GP1 and GP3 samples. The other

mineral phases were only identified once.

107


TABLE 7-1: Mineral phases detected in the geopolymer concretes

Mineral phases Chemical formula GPC GP1 GP2 GP3

Quartz SiO2

Riebeckite Na2(Fe,Mg)3Fe2Si8O22(OH)2

Gypsum CaSO4

Bearsite Be2(AsO4)(OH).4H2O

Beraunite Fe2+

Fe3+

5(OH)5(PO4)4·4H2O)

Lime CaO

Heinrichite Ba(UO2)2(AsO4)2•11H2O

Magnetite Fe3O4

Downeyite SeO2

Guyanaite CrO(OH)

Cadmoselite CdSe

108

7.3 Scanning Electron Microscope (SEM) Analysis

JOEL scanning electron microscope (SEM) model JSM-6480 (FIGURE 7-7)

equipped with energy dispersive x-ray spectroscopy (EDX) was used to characterize the

samples. Imaging of the sample to determine the microstructure was achieved by

irradiating it with focused electron beams from a cathode, detector in the SEM converts

signal emitted by the sample to intensity that produces images of the sample surface

(Chancey, 2008). To avoid distorted images, the sample was coated with Gold (Au), a

conductive material using a sputtering device. Coating is necessary to allow the discharge

of electron build up thereby eliminating charging effect that occurs when the sample is

irradiated with electron beams with high accelerating voltage.

After coating, the sample is placed in the sample chamber which is evacuated to

create a vacuum inside. The sample is then irradiated with electron beam at 7 KV

accelerating voltage and the interaction of sample surface with the electron beams

produces images on the display which was adjusted to X 1,300 magnification to acquire

the SEM images of the sample.

FIGURE 7-7: JOEL SEM equipped with energy dispersive spectrometry (EDX)

109

FIGURES 7-8 to 7-12 show the SEM micrographs of the starting materials and

the produced geopolymer concretes. As shown in FIGURE 7-8, the CFA comprises of

spherical particles with smooth surfaces while the SF is made up of smaller particles that

clump together easily. The CFA has a mean particle size of 47 µm while the SF has mean

particle size of 277 µm.

CFA SF

FIGURE 7-8: SEM micrograph of CFA and SF

Micrograph of the geopolymer concretes (FIGURES 7-9 to 7-12) showed that the

material is very similar in microstructure. It shows a homogenous featureless hydration

product that result from the dissolution of the CFA and SF by the strong alkaline liquid.

110

FIGURE 7-9: SEM micrograph of the GPC geopolymer concrete

FIGURE 7-10: SEM micrograph of the GP1 geopolymer concrete

111



112

From these micrographs, the addition of hydrated lime during the geopolymer

synthesis did not significantly alter the surface morphology of the geopolymer. In all the

geopolymer concrete samples, the dense featureless product is the aluminosilicate matrix

of geopolymer. Unfortunately, there was no observed presence of unreacted or partially

reacted CFA particles which is normally seen in the microstructure of geopolymer.

7.4 Energy Dispersive X-Ray Spectroscopy (EDX) Analysis

Elemental composition of the geopolymer concrete was determined through the

use of the EDX attached to the SEM. According to Chancey (2008), electron beams at

accelerating voltage between 15 KV to 25 KV are normally used to irradiate the sample.

Interaction of these electron beams with the sample generates characteristics X-ray

photons with energies specific to the elements contained in the sample. Detectors in the

EDX detect photons and correlate their respective energies with the elements that emit

them. The EDX spectrums obtained from the EDX analysis are presented in FIGURES 7-

13 to 7-18. As expected, majority of elements identified in all the materials (CFA, SF

and geopolymer samples) are Si, Al, C and O which is due to the aluminosilicate nature

of both the starting materials and produced geopolymer concretes. Unfortunately, the

EDX analysis did not identify the presence of minor elements such as As, Cr and Se

(TABLE 7-2).

113

FIGURE 7-13: EDX spectrum of CFA

FIGURE 7-14: EDX spectrum of SF

FIGURE 7-15: EDX spectrum of GPC

114

FIGURE 7-16: EDX spectrum of GP1



FIGURE 7-18 does not show the presence of Si peak in the EDX spectrum for the

GP3 geopolymer concrete. Tantalum (Ta) peak occurs instead in the spectrum which is

115

due to the overlap between Si-K and Ta-M peaks (Suzuki and Rohde, 2008). Si is the

most probable element that belongs to the peak at 1.7 keV. After quantification of the

element, the normalized bulk composition of the geopolymer concrete is presented in

TABLE 7-2.

TABLE 7-2: Elemental composition of the geopolymer concretes

Elements CFA SF GPC GP1 GP2 GP3

Al 13.25 2.08 5.64 5.53 9.35 3.27

Si 18.60 28.81 29.57 33.76 19.92

O 40.59 34.64 43.92 42.71 25.11 25.68

C 15.74 28.28 11.90 7.69 10.02 38.22

Fe 3.08 2.07 1.97 8.83 1.46

Cu 2.52 2.97 1.86 1.89 9.37 1.57

Ca 1.69 1.15 0.89 4.70 0.51

K 1.66 0.83 0.68 2.16 0.33

Ti 1.15 0.34 1.73 0.19

Mo 1.38

Mg 0.33 0.45 0.51 0.81

Au 3.21 0.31 1.35 3.51

Na 2.41 3.08 3.05 1.46

V 0.53

Ta* 20.22

S 0.19

*Ta presence is the result of overlap between Ta and Si peak at 1.7 KeV

116

7.5 Summary

The result of the XRD investigation is less satisfactory because mineral phases

such as ettringite, monosulfoaluminate, CSH and calcium metalates that are considered

suitable candidate for immobilizing oxyanion elements were not identified in the

geopolymer concretes. This does not mean that these phases are not formed or present in

the samples, the peaks of the mineral phases are most likely not successfully identified

because of low peak intensity and limitation of the AMSCD database used for phase

identification. On the other hand, Van Jaarsveld and Van Deventer (1999) noted that

large part of geopolymer structure is amorphous to X-ray hence the absence of many

crystalline phases. Therefore, the inability to identity mineral such as CSH might be due

to the fact that the mineral is essentially amorphous (Gougar et al., 1996).

From the SEM analysis of the geopolymer concretes, the addition of calcium did

not significantly affect the microstructure of the geopolymer. Although it is believed that

the presence of extra calcium in the form of calcium hydroxide would lead to the

precipitation of poorly crystalline CSH or calcium mineral phases (Temuujin et al.,

2009), these minerals were not seen in the micrographs acquired from the SEM analysis.

CHAPTER 8: SPECIATION MODELING USING PHREEQC/PHREEPLOT

8.1 Background on PHREEQC/PHREEPLOT

PHREEQC is one of the most widely used speciation modeling program, which is

based on the equilibrium of aqueous solutions with mineral phases, solid solutions,

sorbing surfaces and gases (Parkhurst and Appelo, 1999; Halim et al., 2005). The

program uses ion-association aqueous model to calculate the distribution of aqueous

species in any aqueous solution and can allow the concentration of elements to be

adjusted to equilibrium or a specified saturation index (SI). The ion-association model

requires that before chemical equilibrium can be achieved all mass-action equations for

the aqueous species must be satisfied (Parkhurst and Appelo, 1999). PHREEQC program

uses information contained in the associated database and input file to calculate the

distribution of species and saturation indices of mineral phases. The input file contains set

of keywords that define the pH, temperature, density, chemical composition of the

solution (total concentration of cations and anions) while the database file contains

thermodynamic parameters such as dissociation equations and constants, mineral

formation reactions, and temperature functions (Zhu and Anderson, 2002).

PHREEPLOT is a program that has the capability of using output from

PHREEQC to produce high quality geochemical plots. It contains an embedded version

of the PHREEQC program and has the ability to do simple looping which makes it easier

to do repetitive PHREEQC calculations needed to generate a wide range of graphical

118

plots (Kinniburgh and Cooper, 2011). PHREEPLOT also consists of set of keywords in

the input file and associated database which defines the thermodynamic data needed for

the modeling. Information contained in the input file is read and processed simulation by

simulation to calculate the distribution of species and saturation indices of phases. This

chapter focuses on using PHREEPLOT to model the distribution of aqueous species of

As, Cr and Se based on the aqueous solution input data and mineral phases identified as

the solubility controlling phases.

8.1.1 The PHREEPLOT Database

Databases contain definition of chemical species, complexes and dissociation

constants under specified conditions such as temperature (Charlton et al., 1997; Dhir et

al., 2008). Most geochemical modeling programs come with several databases;

PHREEPLOT contains more database than other geochemical modeling programs used in

geochemical modeling. TABLE 8-1 present the databases associated with the

PHREEPLOT program.

TABLE 8-1: Databases associated with PHREEPLOT

TABLE 8-1(continued)

Database Size Description and key features

amm.dat 21 KB Small entries

iso.dat 255 KB Contains common mineral phases

minteq.dat 156 KB Developed for the minteq program and contains

organic compound, uranium minerals, arsenic

minerals, metalates of Ca and other elements

minteqv4.dat 390 KB Updated version with more entries than minteq.dat

NAPSI_290502 117 KB

119

TABLE 8-1(continued)

Database Size Description and key features

phreeqc.dat 34 KB Contains limited but consistent entries

phreeqd.dat 29 KB

pitzer.dat 20 KB

sit.dat 506 KB Contains phases such as ettringite,

monosulfoaluminate, gismondine, hydrogarnet,

downeyite and CSH

wateq4f.dat 99 KB Phreeqc.dat extended with many heavy metals

included

llnl.dat 756 KB A huge database that contains phases such as

gismondine, cadmoselite, downeyite and ettringite

Most of the databases do not contain dissociation constant and dissolution

equation for all the aqueous species or mineral phases needed for the simulation. Some

mineral phase of interest is missing in the database, their information was manually

adding into the chosen database via the input file data. These supplementary data for

mineral phases were obtained from literature search and other database.

8.1.2 Description of the PHREEPLOT Input File

As discussed in section 8.1, data needed for the modeling are supplied via the

input file. This input file contains set of keywords that is followed by data blocks which

define the parameters needed in the modeling separated into simulations by the END

keyword (Kinniburgh and Cooper, 2011). END keyword literally instructs the program to

calculate. Each keyword signifies the beginning of data block and the program knows

120

what to do with the data that follows the keyword provided the keyword is written

correctly (Zhu and Anderson, 2002). The input file is separated by the CHEMISTRY

keyword. The top of the input file contains PHREEPLOT settings while the bottom

contains the PHREEQC code (Kinniburgh and Cooper, 2011). The CHEMISTRY

keyword is used to separate the two section of the input file i.e. it signifies the beginning

of the PHREEQC input. According to Kinniburgh and Cooper (2011), PHREEPLOT

input file should be kept as simple as possible and preliminary calculations should be

placed at the beginning of the file.

Some of the keywords relevant for this modeling are discussed further in this

section. INCLUDE is a keyword that is placed in the CHEMISTRY section which is used

to call other files that contain codes needed for several calculations. Two INCLUDE files

relevant for this modeling are ―speciesvsph.inc‖ and ―speciesvspht.inc‖. These two files

are used in making the species vs pH plots; the former plots the relative concentration (in

%) of all species while the later plots the overall percentage of the elements species that

is in dissolved form (Kinniburgh and Cooper, 2011). The SOLUTION keyword defines

the composition of the aqueous solution which includes temperature, pH and density.

PHASES defines name, dissociation reactions and thermodynamic data for minerals and

gases that are used in the speciation and batch-reaction calculations (Parkhurst and

Appelo, 1999). EQUILIBRIUM_PHASES is used to define the combination of minerals

and /or gases that react reversibly with the aqueous solution to equilibrium, prescribed

saturation index (SI) or gas partial pressure (Parkhurst and Appelo, 1999; Appelo and

Postma, 2005).

121

8.2 Procedure for the PHREEPLOT Speciation Modeling

Four different sets of simulations with PHREEPLOT are performed in this study.

The pH temperature and chemical composition of the aqueous solutions from the WLT

performed on the geopolymer concretes (section 6.5) were used in each simulation.

Before the preparation of the input file, a suitable database was chosen that contains (1)

aqueous species of the elements of interest (2) dissolution equations of mineral phases

that are considered solubility controlling mineral phases (3) most accurate solubility

constant (k) for the mineral phases and aqueous species. The ‗llnl.dat‘ thermodynamic

database was employed because it is the largest and contains huge amount of mineral

phases that can potentially be solubility controlling phases.

The input file was then prepared by using keywords and associated data blocks.

The PHREEPLOT section of the input file begins with the keyword SPECIATION and

contains data blocks that define the database used, calculation type ‗species‘, the

calculation method, elements of interest, behavior of the program when an error is

encountered, looping function and number of times to loop. This section also contains

information on how the program handles and plots the generated data. The CHEMISTRY

keyword signifies the beginning of the PHREEQC section. In this section, the solubility

controlling minerals phases that are not present in the ‗llnl.dat‘ database were manually

added. TABLE 8-2 shows the manually added mineral phases, their dissolution equations

and solubility constant. Compositions of the aqueous solution (TABLE 6-5 to 6-7) used

in the speciation calculation are also entered in this section and the input file saved with a

―.ppi‖ extension in a designated folder. Appendix F contains the input file for one of the

simulations while the corresponding output file is in appendix G.

122

TABLE 8-2: Mineral phases manually added to the simulation


Phase name Dissolution equation and log_k at 25oC references

2

Cr-ettringite Ca6(Al(OH)6)2(CrO4)3:26H2O

= 6Ca2+

+2Al3+

-12H++3CrO4

2-+38H2O

log_k 60.28

sit.dat

Se-ettringite Ca6(Al(OH)6)2(SeO4)3:31.5H2O =

6Ca2+

+2Al3+

+3SeO42-

-12H+ +43.5H2O

log_k 61.29

(Chrysochoou

and Dermatas,

2006)

Se-monosulfoaluminate Ca4(Al(OH)6)2SeO4:9H2O = 4Ca2+

+2Al3+

-12H+ +SeO4

2- +21H2O

log_k 73.40

(Cornelis et al.,

2008)

Monosulfoaluminate Ca4Al2(SO4)(OH)12:6H2O = 4Ca2+

+2Al3+

-12H+ +SO4

2- +18H2O

log_k 72.73

sit.dat

Cr-monosulfoaluminate Ca4Al2O6(CrO4):15H2O=4Ca2+

+2Al3+

-12H+ +CrO4

2- +21H2O

log_k 71.36

sit.dat

CaSeO4:2H2O CaSeO4:2H2O = Ca2+

+SeO42-

+2H2O

log_k -2.68

sit.dat

CaSeO3:2H2O CaSeO3:2H2O = Ca2+

+SeO32-

+ 2H2O

log_k -4.6213

(Cornelis et al.,

2008)

CaSeO4 CaSeO4 = Ca2+

+SeO42-

2 sit.dat is a thermodynamic database in PHREEPLOT

123


Phase name Dissolution equation and log_k at 25oC references

2

log_k -3.0900

Ca3(AsO4)2:3H2O Ca3(AsO4)2:3H2O = 3Ca2+

+ 2AsO43-

+3H2O log_k -21.14

(Cornelis et al.,

2008)

CaHAsO3 CaHAsO3 = Ca2+

+HAsO32-

log_k -6.52

(Cornelis et al.,

2008)

CaCrO4 CaCrO4 = Ca2+

+CrO42-

log_k -3.15

sit.dat

CaHAsO4 CaHAsO4 = Ca2+

+ HAsO42-

Log_k -2.66

(Alexandratos

et al., 2007)

8.3 Model Simulation Results and Interpretation

Plots that show the distribution of species of the three elements are discussed in

this section. FIGURES 8-1 to 8-3 showed the percentage distribution of species of each

element as a function of pH. It is evident from the plots that the predominant species

varies across the pH range.

The simulation results of As shown in FIGURE 8-1 reveal that HAsO3F- and

AsO3F2-

are the As species present in the aqueous solution from all the geopolymer

concretes. HAsO3F- is the dominant specie in the acidic pH range while AsO3F

2- is more

dominant in the alkaline pH. These species of As are As (5) which is less soluble and less

toxic than As (3) (Moon et al., 2004). At about pH 6, the proportion of the two species in

the solution is the same.

124

FIGURE 8-1: Typical distribution of As species from the PHREEPLOT simulation

As shown in FIGURE 8-2, SeO42-

and HSeO4- are two species of Se (6) that are

present in the aqueous solution in considerable amount. From pH 1 to pH 2, HSeO4- is the

dominant specie present in the solution and as pH increases from 2, the dominant specie

changes to SeO42-

. At around pH 2, the two species have equal amount in the solution. Se

(4) species such as SeO32-

, HSeO3- and H2SeO3 are also present in the solution but the

amount present is so small that it does not significantly contribute to the species

distribution. The type of Se present in the solution in considerable amount is less toxic

since Se(4) is considered to be more toxic than Se (6) (Goldberg et al., 2006).

125

FIGURE 8-2: Typical distribution of Se species from the PHREEPLOT simulation

Both Cr (3) species: Cr3+

, CrOH2+

, CrCl2+ and Cr (6) species: HCrO4

-, CrO4

2- are

responsible for the distribution of Cr in the aqueous solution. Some of these species have

very low amount and therefore have insignificant contribution to the Cr distribution. The

obviously dominant species are Cr3+

, HCrO4- and CrO4

2-. Between pH 1 and pH 1.5, Cr

3+

is the main specie while HCrO4- is the other specie present. Equal amount of these two

species exist at pH 1.5, afterwards HCrO4- becomes the dominant specie and Cr

3+ reduces

to zero. The amount of the HCrO4- specie starts to diminish at around pH 5 while CrO4

2-

starts to increase. At around pH 7, there was equal distribution of the HCrO4- and CrO4

2-

specie. In the alkaline pH range, the dominant specie is the CrO42-

. Among all the species

present in the solution, the Cr(6) species are considered to be more toxic than Cr(3)

species (Shtiza et al., 2009).

126

FIGURE 8-3: Typical distribution of Cr species from the PHREEPLOT simulation

8.4 Validation of the Model Output

The purpose of model validation is to check the ability of the model to correctly

and realistically predict the results. Due to lack of experimental data from literature

search to use for validation of the model, the validation was instead conducted by

comparing the calculated molal concentration of each element (appendix G for molal

concentration at pH 11.23) obtained from the simulations with the measured

concentration in the aqueous solution used as input data. TABLE 8-3 contains the

comparison between the measured concentration and molal concentration obtained from

the modeling. Overall, the calculated concentration of As, Cr and Se from the model is

relatively very close to the measured concentration from the WLT that was used as input

data.

127

TABLE 8-3: Comparison of input and PHREEPLOT model output concentration Concentration (mg/l)

GPC GP1 GP2 GP3

PHREEPLOT WLT PHREEPLOT WLT PHREEPLOT WLT PHREEPLOT WLT

As 1.027 1.023 1.023 1.019 1.019 1.015 0.928 0.955

Cr 0.011 0.025 0.011 0.025 0.011 0.025 0.011 0.025

Se 0.407 0.405 0.420 0.418 0.424 0.422 0.375 0.374

8.5 Summary

The PHREEPLOT simulations showed the oxyanion elements (As, Cr, Se) are

present in the leachates in As(5), Se(6), Cr(3) and Cr(6) oxidation states. The results

indicated that in the alkaline pH range, As (5) exist mainly as AsO3F2-

, Se(6) as SeO42-

and Cr(6) as CrO42-

. These As and Se species present in this aqueous solution are in the

higher oxidation states and are less toxic than the reduced form. Cr on the other hand,

exists in an oxidation state that is found in the alkaline pH range is considered to be the

most toxic form. However the distribution of this higher oxidation states chromium

(Cr(6)) is negligible in the alkaline pH range.

CHAPTER 9: CONCLUSIONS AND RECOMMENDATIONS

9.1 Conclusions

As stated in chapter one, the suitability of geopolymer as a safe alternative to

cement in construction and waste stabilization depends on the material potential

environmental impacts. There is thus a need to properly understand geopolymer leaching

behavior during its service life and end of life conditions. The leaching of oxyanion

forming elements such as As, Cr and Se was particularly important because these

elements can exist in oxidation states that are more mobile in the alkaline pH

environment that would exist in geopolymer pore solution. This dissertation was set up

with the aim of understating the leaching mechanism oxyanion forming elements (As, Cr,

Se) from fly ash based geopolymer concrete and investigates the effect of hydrated lime

on mobility of these elements from the material and strength of the concrete. To achieve

the research goals, specific objectives (Section 1.4) were set and hypothesis (Section 1.5)

formulated. Several experimental tasks were designed in the course of this dissertation.

The following conclusions have been made based on the results from the tasks presented

in preceding chapters of this dissertation.

9.1.1 Synthesis of Geopolymer Concrete

Geopolymer concretes were synthesized using CFA, SF, CA, FA, NaOH with

varying amount of hydrated lime, cured without heat at room temperature and in an oven

129

maintained at 75oC. Major findings from the geopolymer concrete synthesis are

summarized as follows:

Geopolymer concretes are alkaline material with pH greater than 11 and the same

bulk density as normal weight concrete (2300 kg/m3) which is expected since

aggregates determine the weight of concrete.

The 28 days compressive strength of geopolymer concretes cured without heat is

relatively lower than the strength of the concrete cured at 75oC. The average

strength of the concretes cured without heat varies from 13 MPa (1937 psi) to 18

MPa (2647 psi) while the heat cured geopolymer concretes have average strength

that varies from 42 MPa (6013 psi) to 56 MPa (8117psi).

There is presence of efflorescence on the surface of the geopolymer concretes

cured without heat which might indicate insufficient geopolymerization hence the

lower strength of the concrete when compared with the heat cured geopolymer.

Hydrated lime addition leads to reduction in strength of the geopolymer concretes.

Geopolymer concretes made with additional hydrated lime exhibit lower

compressive strength than the control geopolymer concrete that has zero hydrated

lime added (GPC).

Among the geopolymer concrete with hydrated lime, the GP2 with 1% hydrated

lime have the highest strength in both the concrete cured with heat and without

heat.

The lower compressive strength of the geopolymer concrete cured without heat

makes it suitable for use only in low strength structural applications such as walkway,

road divider and solidification of waste. The heat cured geopolymer concrete on the hand

130

can be used for higher strength structural applications similar to OPC concrete since it

has compressive strength that exceed 41 MPa (6000 psi). It is evident from this

investigation that heat curing is required in order to produce geopolymer concrete of

considerable compressive strength. There is also an optimal amount of additive such as

hydrated lime that can added to geopolymer concrete that would not affect the strength of

the material. Part of hypothesis 5 which states that ―leaching of these oxyanion forming

elements can be mitigated by the addition of extra calcium in the form of lime during

geopolymer synthesis, which would lead to the formation of oxyanion substituted

calcium mineral phases in addition to the geopolymer phase without affecting the

durability of the geopolymer‖ was tested in Section 5.3. The results show that even

though the addition of lime lead to reduction in compressive strength of the geopolymers,

the overall the minimum compressive strength of the geopolymers that contain additional

lime still meets the strength requirement for concrete used in high strength structural

applications.

9.1.2 Leaching of Elements from Geopolymer Concrete

The leaching tests performed on the geopolymer concretes are: pH dependence

test, Dutch availability test, water leach test (WLT) on the granular form of the concretes

and the tank test on the monolith form of the concretes. Hypothesis 2 which states that

―oxyanion forming elements exhibit different leaching behavior than other elements that

are leached from the alkaline fly ash based geopolymer‖ was addressed using the pH

dependence test presented in Section 6.2. Results obtained from the pH dependence test

indicate that all oxyanion forming elements (As, Se, Mo and V) except Cr displays higher

mobility in the alkaline pH. Cr and other elements such as Al, Ca, Fe, Mg, B, Ba, Cu,

131

Mn, and Zn exhibit different leaching behavior with their highest mobility occurring in

the acidic pH range. Elements that include Al, Si, Ca and Na have extremely high

mobility from all the geopolymer concretes. The test also supported hypothesis 1 which

states that ―oxyanion elements (As, Cr, Se) are present in leachates from fly ash based

geopolymer concrete‖. In both the acidic and alkaline pH range, mobility of most of the

elements (As, Se, Mo, V, Si, Al, Fe, Mg, Cu, Mn and Zn) is lowest in the GP2 concrete

that has 1% hydrated lime. This implies that the addition of 1% hydrated lime was able to

reduce the mobility of most of the elements from the geopolymer concrete.

Hypothesis 3 which states that ―standard leaching test methods conducted at a

neutral pH are adequate for predicted the leaching of oxyanion forming elements‖ was

tested in Section 3.6.2 by statistically comparing the result of the Dutch availability test

conducted at neutral pH and acidic pH with result obtained from a modification of the

availability test conducted at the material pH and acidic pH. No statistical difference was

observed between the results from the two test methods, which signifies that the Dutch

test conducted at neutral pH is adequate to predict leaching of the oxyanion forming

elements (As, Cr, Se) from the alkaline fly ash based geopolymer.

The Dutch availability test used to investigate the leaching from the fly ash based

geopolymer concrete under the worst case scenario showed that As and Se exhibit

considerable leachability from the geopolymer concretes. As mobility varies from 8.3

mg/kg to 9.7 mg/kg while the mobility of Se range between 2.9 mg/kg to 4.5 mg/kg. The

lowest amount of each element leached (As – 8.3 mg/kg, Se – 2.9 mg/kg) occurs in the

GP2 sample. The amount of Cr released from all the geopolymer concrete is constant.

132

This results suggest that 1% hydrated lime in the geopolymer concrete may lead to

reduction in mobility of As and Se.

Tank test conducted on the monolithic geopolymer concrete better represent the

leaching behavior of the material during its service life. The test results showed that the

release mechanisms associated with the leaching of the three elements are surface wash-

off, diffusion, depletion and dissolution. Surface wash-off, diffusion and depletion are the

main leaching mechanism responsible for the leaching of As and Se which have high or

moderate mobility that tends to a flat plateau as the leaching duration increases. This

signifies that the element is depleting in the matrix. Cumulative amount of As released

from the geopolymer concretes reached a maximum of 300 mg/m2 while that of Se

reached a maximum of 130 mg/m2. The leaching mechanisms associated with the release

of Cr are surface wash-off, diffusion and dissolution with a cumulative amount of Cr

released at the end of the leaching duration that reached 3 mg/m2. It is obvious from the

result that the cumulative mobility of Cr has not reached the depletion stage because the

element have lower mobility rate than the other elements. Overall, the mobility of As and

Se from the GP2 concrete with 1% hydrated lime is the lowest.

Hypothesis 5 which states that ―leaching of these oxyanion elements can be

mitigated by the addition of extra calcium in the form of lime during geopolymer

synthesis‖ was tested using the pH dependence test (Section 6.2), Dutch availability test

(Section 6.3) and the tank test (Section 6.4). The results reveal that at 1.0% lime addition

there was reduction in the mobility of most of the elements including the oxyanion

forming elements (As, Cr, Se).

133

9.1.3 XRD and SEM/EDX Analysis of the Geopolymer Concretes

Hypothesis 4 which states that ―calcium containing mineral phases such as

ettringite, hydrocalumite, monosulfoaluminate, calcium metalates and calcium silicate

hydrates (CSH) are effective for immobilizing oxyanion forming elements via ion

substitution‖ was tested in Section 7.2 and 7.4. Although literature search suggested that

mineral phases such as ettringite, monosulfoaluminate, CSH and precipitates of calcium

are solubility controlling phases that can help reduce the mobility of the oxyanion

forming elements like As, Se and Cr. Unfortunately, this hypothesis cannot be supported

due to lack of identification of the mineral phases in the geopolymer concrete samples

analyzed. Mineralogical analysis of the geopolymer concrete using the XRD did not

reveal the presence of these solubility controlling mineral phases, but however reveals the

presence of other minerals phases such as quartz, riebeckite, gypsum, bearsite, bearunite,

lime, downeyite, cadmoselite, heinrichite, guyannaite and magnetite. Quartz is the only

mineral that is common to all the geopolymer concretes. The mineral beraunite was found

in the GP1 and GP3 concrete while the remaining minerals are found only in one

geopolymer concrete sample. The inability of the mineralogical analysis to identify the

solubility controlling mineral phases is most likely due to the fact that geopolymer

concrete are essentially amorphous to x-ray detection or due to low peak intensity which

makes their identification impossible.

Microstructural analysis of the geopolymer concrete using SEM showed that the

materials have similar surface morphology. All the geopolymer concretes have

homogenous featureless hydration product. It is obvious that the additional hydrated lime

did not significantly affect the microstructure of the concretes.

134

9.1.4 Distribution of Species of As, Cr and Se

PHREEQC/PHREEPLOT simulation identified HAsO3F- and AsO3F

2- are the As

species present in the aqueous solution while SeO42-

and HSeO4- are two species of Se

present in the aqueous solution in considerable amount. This species of As and Se are

respectively in the As (5) and Se(6) oxidation states which are considered to be less toxic

than the reduced oxidation state of the elements (As(3) and Se(4)). Dominant Cr species

present in the aqueous solution include Cr3+

, HCrO4- and CrO4

2-. Cr

3+ is in the Cr(3)

oxidation state while HCrO4- and CrO4

2- are in Cr(6) oxidation state. Cr(6) is considered

to be more toxic than Cr(3). In the alkaline pH, AsO3F2-

, SeO42-

, and CrO42-

are the main

species present in the aqueous solution. The closeness of the concentration of elements

used in input data and the calculated concentration from PHREEQC/PHREEPLOT

simulation was assessed. This comparison showed that the concentrations were very close

which means that the model was able to predict the concentration of As, Cr and Se in the

aqueous solution.

9.1.5 Overall Conclusions

The objectives of the research are listed below and the conclusions derived from

results of various experiment conducted to meet these objectives are stated.

To determine the release of oxyanion elements (As, Cr, Se) from fly ash based

geopolymer concrete under service life (monolithic) and end of life (granular)

conditions using appropriate tests.

To determine the maximum amount of oxyanion forming elements that would be

released under the worst case scenario when the material is pulverized.

135

The pH dependence, Dutch availability (worst case scenario) and tank (service

life) test were used to determine the mobility of the elements from the fly ash

based geopolymer concretes. The leaching tests reveal that As and Se leach out

from the geopolymer concrete samples in the high alkaline range (pH >11) in

greater amount during the service life and end of life conditions.

To assess the potential to decrease mobility, or even total immobilization of

oxyanion element (As, Cr, Se) in geopolymer concrete by means of using

hydrated lime as an admixture.

The addition of about 1% hydrated lime to geopolymer concrete led to reduction

in the mobility of As and Se. The added hydrated lime also led to overall

reduction in compressive strength of the geopolymer concretes but when

concretes with hydrated lime additive were compared, the concrete with 1%

hydrated lime result in slight increase in the compressive strength of the

geopolymer concrete.

To determine if there is formation of calcium containing mineral phases, calcium

precipitates or calcium metalates in the produced geopolymer concrete.

XRD analysis of the geopolymer concrete did not reveal the presence of these

mineral phases, but minerals phases such as quartz, riebeckite, gypsum, bearsite,

bearunite, lime, downeyite, cadmoselite, heinrichite, guyannaite and magnetite

were identified in the geopolymer concretes.

To identify the probable mechanisms responsible for immobilization of the

oxyanion forming elements (if there is any immobilization).

136

Although there was observed reduction in the mobility of the oxyanion forming

elements (As, Cr, Se) when 1% hydrated lime was added to the geopolymer

concrete. The mechanisms responsible for the immobilization were not known

due to the absence of the solubility controlling mineral phases that should

immobilize the elements via ion substitution and precipitation.

To determine the species of the oxyanion elements (As, Cr, Se) released from fly

ash based geopolymer concrete and their potential environmental impacts.

Even though there is high mobility of As and Se from the geopolymer, the species

of the elements identified by geochemical modeling indicated that their mobility

would not cause adverse environmental issue since these species belong to

oxidation states that are less toxic, while in the case of Cr mobility results in

release of low concentration of elements below the MCL.

Based on the results from this dissertation, more extensive investigation is needed

on mobility of oxyanion forming elements from geopolymer concrete before deciding

whether the material can be safely used in place of Portland cement concrete. However,

the results suggest that the material can be used in solidification/ stabilization of waste

before landfilling since the amount of oxyanion elements (As, Cr, Se) released is less

than the amount specified in the TCLP test as regulatory limits.

9.2 Limitations of the Study

Although most of the research objectives and hypotheses were reached, there are

some limitations and number of issues that are not properly addressed due to equipment

and time constraints. First, some of the tests were performed in only duplicates. It would

be advantageous to increase the number of replicates to five in order to be able to perform

137

proper statistical analysis of the results. Second, the free mineral phase identification

software and the AMSCD mineral database is not very reliable due to the limited number

of entries in the database and reduced functionality of the free software. Finally,

speciation modeling is not enough in the determination of the species of oxyanion

forming elements (As, Cr, Se) released from the geopolymer concretes.

9.3 Recommendations for Future Work

The following recommendations are suggested for future work:

Leaching behavior, mineralogical and microstructural analysis of the geopolymer

concrete cured without heat should be studied.

An optimized mix design with enough additives that would ensure the formation

and presence of the solubility containing mineral phases.

More extensive XRD mineral database should be used for identification of the

mineral phases present in the geopolymer concrete.

Platinum coating can be used instead of gold before the SEM/EDX analysis in

order to reduce the occurrence of charging and the ability to detect elements that

are identified at high accelerating voltage.

Speciation analysis using a combination of IC and ICP-MS should be conducted

to confirm the presence of the less toxic oxidation state of As, Cr and Se.

Accuracy of the result obtained from the PHREEPLOT modeling should be

verified using the result from speciation analysis using experimental method.

Future research should be done to establish the relationship between the strength

of the geopolymer concretes and the leachability of the oxyanion forming trace

elements (As, Cr, Se).

138

REFERENCES

ACAA. 2003. Fly ash facts for highway engineers Report No: FHWA-IF-03-019

American Coal Ash Association, Aurora, Colorado.

ACAA. 2008. Sustainable construction with coal combustion products:A primer for

architects, American Coal Ash Association Educational Foundation American

Coal Ash Association, Aurora, Colorado.

Alexandratos, V.G., E.J. Elzinga, and R.J. Reeder. 2007. Arsenate uptake by calcite:

Macroscopic and spectroscopic characterization of adsorption and incorporation

mechanisms. Geochimica et Cosmochimica Acta, 71 (17):4172-4187.

Allen, T. 2003. Powder sampling and particle size determination. Amsterdam; Boston:

Elsevier.

Andrews, L.C. 2007. A geochemical analysis of aluminum hydroxides and iron oxides in

little backbone creek, Shasta county, California. Bachelor of Arts, Carleton

College, Northfield, Minnesota.

Appelo, C.A.J., and D. Postma. 2005. Geochemistry, groundwater and pollution. 2nd ed.

Leiden, The Netherlands: A.A. Balkema publishers.

ASTM. 2003. ASTM C702 - Standard practice for reducing samples of aggregate to

testing size, ASTM International, West Conshohocken, PA.

ASTM. 2006a. ASTM C136 - Standard test method for sieve analysis of fine and coarse

aggregates, ASTM International, West Conshohocken, PA.

ASTM. 2006b. ASTM C207 - Standard specification for hydrated lime for masonary

purposes, ASTM International, West Conshohocken, PA.

ASTM. 2006c. ASTM D3987 - Standard test method for shake extraction of solid waste

with water, ASTM International, West Conshohocken, PA.

ASTM. 2008. ASTM C618 - Standard specification for coal fly ash and raw or calcined

natural pozzolan for use in concrete, ASTM International, West Conshohocken,

PA.

ASTM. 2010a. ASTM C39 - Standard test method for compressive strength of cylindrical

concrete specimens, ASTM International, West Conshohocken, PA.

ASTM. 2010b. ASTM C1240 - Standard specification for silica fume used in

cementitious mixtures, ASTM International, West Conshohocken, PA.

B'Hymer, C., and J.A. Caruso. 2006. Selenium speciation analysis using inductively

coupled plasma-mass spectrometry. Journal of Chromatography A, 1114 (1):1-20.

139

Badur, S., and R. Chaudhary. 2008. Utilization of hazardous wastes and by-products as a

green concrete material through S/S process: A review. Reviews on Advanced

Materials Science, 17 (1-2):42-61.

Bankowski, P., L. Zou, and R. Hodges. 2004. Reduction of metal leaching in brown coal

fly ash using geopolymers. Journal of Hazardous materials, 114 (1-3):59-67.

Barnhart, J. 1997. Occurrences, uses, and properties of chromium. Regulatory

Toxicology and Pharmacology, 26 (1):S3-S7.

Baur, I., P. Keller, D. Mavrocordatos, B. Wehrli, and C.A. Johnson. 2004. Dissolution-

precipitation behaviour of ettringite, monosulfate, and calcium silicate hydrate.

Cement and Concrete Research, 34 (2):341-348.

Beckman Coulter. 2011. LS 13 320 Laser diffraction particle size analyzer instructions

for use, Beckman Coulter, Inc, Brea, CA.

Bin-Shafique, M.S. 2002. Leaching of heavy metals from fly ash stabilized soils. PhD

Dissertation, University of Wisconsin-Madison, Madison, Wisconsin.

Bond, M.M. 2000. Characterization and control of selenium releases from mining in the

Idaho phosphate region. M.S Thesis, Environmental Science, Moscow, Idaho.

Bone, B.D., L.H. Barnard, D.I. Boardman, P.J. Carey, C.D. Hills, H.M. Jones, C.L.

Macleod, and M. Tyrer. 2004. Review of scientific literature on the use of

stabilisation/solidification for the treatment of contaminated soil, solid waste and

sludges, Environment Agency, Bristol, United Kingdom.

Bremner, T. 2001. Environmental aspects of concrete: problems and solutions. 1st All-

Russian Conference on Concrete and Reinforced Concrete, Moscow, Russia, 232-

246

Cappuyns, V., and R. Swennen. 2008. The application of pHstat leaching tests to assess

the pH-dependent release of trace metals from soils, sediments and waste

materials. Journal of Hazardous materials, 158 (1):185-195.

CEN. 2006. TS 14997 - Characterization of waste. Leaching behaviour tests. Influence of

pH on leaching with continuous pH-control European committee for

standardization (CEN), Brussels, Belgium.

Chancey, R.T. 2008. Characterization of crystalline and amorphous phases and respective

reactivities in a class F fly ash. PhD dissertation, University of Texas at Austin,

Austin, Texas.

Charlton, S.R., C.L. Macklin, and D.L. Parkhurst. 1997. PHREEQCI—a graphical user

interface for the geochemical computer program PHREEQC. Water Resources

Investigation Report: 97-4222.

140

Chrysochoou, M., and D. Dermatas. 2006. Evaluation of ettringite and hydrocalumite

formation for heavy metal immobilization: Literature review and experimental

study. Journal of Hazardous materials, 136 (1):20-33.

Cioffi, R., L. Maffucci, and L. Santoro. 2003. Optimization of geopolymer synthesis by

calcination and polycondensation of a kaolinitic residue. Resources, conservation

and recycling, 40 (1):27-38.

Cornelis, G., C.A. Johnson, T.V. Gerven, and C. Vandecasteele. 2008. Leaching

mechanisms of oxyanionic metalloid and metal species in alkaline solid wastes: A

review. Applied Geochemistry, 23 (5):955-976.

Damtoft, J.S., J. Lukasik, D. Herfort, D. Sorrentino, and E.M. Gartner. 2008. Sustainable

development and climate change initiatives. Cement and Concrete Research, 38

(2):115-127.

Das, G.P. 2008. Ash weathering controls on contaminant leachability. PhD dissertation,

Infrastructure and Environmental Systems, The University of North Carolina at

Charlotte, Charlotte, North Carolina.

Davidovits, J. 1991. Geopolymers : Inorganic polymeric new materials. Journal of

thermal analysis, 37:1633-1656.

Dermatas, D., D.H. Moon, N. Menounou, X. Meng, and R. Hires. 2004. An evaluation of

arsenic release from monolithic solids using a modified semi-dynamic leaching

test. Journal of Hazardous materials, 116 (1):25-38.

Dhir, R.K., T.D. Dyer, and L.J. Csetenyi. 2008. NORA: Non-radioactive waste

solidification methods and stability assessment, Concrete Technology Unit,

Department of Civil Engineering, University of Dundee, Dundee, Scotland.

Diaz, E., E. Allouche, and S. Eklund. 2010. Factors affecting the suitability of fly ash as

source material for geopolymers. Fuel, 89 (5):992-996.

Dogan, O., and M. Kobya. 2006. Elemental analysis of trace elements in fly ash sample

of Yatağan thermal power plants using EDXRF. Journal of Quantitative

Spectroscopy and Radiative Transfer, 101 (1):146-150.

Duxson, P., A. Fernâandez-Jimâenez, J. Provis, G. Lukey, A. Palomo, and J. Deventer.

2007. Geopolymer technology: the current state of the art. Journal of Materials

Science, 42 (9):2917-2933.

EA. 2005a. EA NEN 7371 - The determination of the availability of inorganic

components for leaching - "the maximum availability leaching test",

Environment Agency, United Kingdom.

EA. 2005b. EA NEN 7375 - Determination of leaching of inorganic components with the

diffusion test -The tank test, Environment Agency, United Kingdom.

141

Fällman, A.-M. 1997. Performance and design of the availability test for measurement of

potentially leachable amounts from waste materials. Environmental Science and

Technology, 31 (3):735-744.

Fernández-Jiménez, A., I. García-Lodeiro, and A. Palomo. 2007. Durability of alkali-

activated fly ash cementitious materials. Journal of Materials Science, 42

(9):3055-3065.

Fernández-Jiménez, A., and A. Palomo. 2005. Composition and microstructure of alkali

activated fly ash binder: Effect of the activator. Cement and Concrete Research,

35 (10):1984-1992.

Fernández-Jiménez, A., and A. Palomo. 2009. Nanostructure/microstructure of fly ash

geopolymers. In Geopolymers: structure, processing, properties and industrial

applications, edited by J. L. Provis and J. S. J. van Deventer. Cambridge, United

Kingdom: Woodhead Publishing limited.

Finkelman, R.B., and M.E. Mrose. 1977. Downeyite, the first verified natural occurrence

of SeO. American Mineralogist, 62:316-320.

Gartner, E. 2004. Industrially interesting approaches to "low-CO2" cements. Cement and

Concrete Research, 34 (9):1489-1498.

Giannopoulou, I.P., and D. Panias. 2007. Structure, design and applications of

geopolymeric materials. 3rd International Conference on Deformation Processing

and Structure of Materials, Belgrade, Serbia,

Goldberg, S., D.A. Martens, H.S. Forster, and M. Herbel. 2006. Speciation of selenium

(IV) and selenium (VI) using coupled ion chromatography—hydride generation

atomic absorption spectrometry. Soil Science Society of America Journal, 70

(1):41-47.

Gougar, M., B. Scheetz, and D. Roy. 1996. Ettringite and C---S---H Portland cement

phases for waste ion immobilization: A review. Waste Management, 16 (4):295-

303.

Guo, X., H. Shi, L. Chen, and W.A. Dick. 2010. Alkali-activated complex binders from

class C fly ash and Ca-containing admixtures. Journal of Hazardous materials,

173 (1-3):480-486.

Halim, C.E., S.A. Short, J.A. Scott, R. Amal, and G. Low. 2005. Modelling the leaching

of Pb, Cd, As, and Cr from cementitious waste using PHREEQC. Journal of

Hazardous materials, 125 (1-3):45-61.

Hardjito, D., and V. Rangan. 2005. Development and properties of low-calcium fly ash-

based geopolymer concrete, Research Report GC 1, Curtin University of

Technology, Perth, Australia.

142

Hardjito, D., and M. Tsen. 2008. Strength and thermal stability of fly ash based

geopolymer mortar. The 3rd Asian Concrete Federation international conference

ACF/VCA 2008, 11-13 November, 2008, Ho Chi Minh City, Vietnam,

Iwashita, A., T. Nakajima, H. Takanashi, A. Ohki, Y. Fujita, and T. Yamashita. 2007.

Determination of trace elements in coal and coal fly ash by joint-use of ICP-AES

and atomic absorption spectrometry. Talanta, 71 (1):251-257.

Izquierdo, M., and X. Querol. 2011. Leaching behaviour of elements from coal

combustion fly ash: An overview. International Journal of Coal Geology.

Izquierdo, M., X. Querol, J. Davidovits, D. Antenucci, H. Nugteren, and C. Fernández-

Pereira. 2009. Coal fly ash-slag-based geopolymers: Microstructure and metal

leaching. Journal of Hazardous materials, 166 (1):561-566.

Izquierdo, M., X. Querol, C. Phillipart, D. Antenucci, and M. Towler. 2010. The role of

open and closed curing conditions on the leaching properties of fly ash-slag-based

geopolymers. Journal of Hazardous materials, 176 (1-3):623-628.

Jackson, B.P. 1998. Trace element solubility from land application of fly ash/organic

waste mixtures with emphasis on arsenic and selenium speciation. PhD

dissertation, University of Georgia, Athens, Georgia.

Jankowski, J., C.R. Ward, D. French, and S. Groves. 2006. Mobility of trace elements

from selected Australian fly ashes and its potential impact on aquatic ecosystems.

Fuel, 85 (2):243-256.

Jegadeesan, G., S.R. Al-Abed, and P. Pinto. 2008. Influence of trace metal distribution on

its leachability from coal fly ash. Fuel, 87 (10):1887-1893.

Juenger, M.C.G., F. Winnefeld, J.L. Provis, and J.H. Ideker. 2010. Advances in

alternative cementitious binders. Cement and Concrete Research, - Article in

press.

Khale, D., and R. Chaudhary. 2007. Mechanism of geopolymerization and factors

influencing its development: a review. Journal of Materials Science, 42 (3):729-

746.

Kinniburgh, D., and D. Cooper. 2011. PhreePlot Guide : creating graphical output with

PHREEQC. http://www.phreeplot.org/ (accessed 4th November 2011).

Klemm, W.A. 1998. Ettringite and oxyanion-substituted ettringites-- their

characterization and applications in the fixation of heavy metals: A synthesis of

the literature, Portland Cement Association (PCA), Stokie, Illinois.

Komnitsas, K., and D. Zaharaki. 2007. Geopolymerisation: A review and prospects for

the minerals industry. Minerals Engineering, 20 (14):1261-1277.

http://www.phreeplot.org/

143

Kong, D.L.Y., and J.G. Sanjayan. 2010. Effect of elevated temperatures on geopolymer

paste, mortar and concrete. Cement and Concrete Research, 40 (2):334-339.

Kosson, D.S., H.A. van der Sloot, F. Sanchez, and A.C. Garrabrants. 2002. An integrated

framework for evaluating leaching in waste management and utilization of

secondary materials. Environmental Engineering Science, 19 (3):159-204.

Lloyd, N.A., and B.V. Rangan. 2010. Geopolymer concrete with fly ash. 2nd

International Conference on Sustainable Construction Materials and

Technologies, Ancona, Italy,

Magalhães, M.C.F. 2002. Arsenic. An environmental problem limited by solubility. Pure

and Applied Chemistry, 74 (10):1843-1850.

Mehta, P.K., and P.J.M. Monteiro. 2006. Concrete : microstructure, properties, and

materials. New York: McGraw-Hill.

Min, J.H. 1997. Removal of arsenic, selenium and chromium from wastewater using

Fe(III) doped alginate gel sorbent. PhD dissertation, Civil Engineering, University

of California, Los Angeles, California.

Miyano, T., and C. Klein. 1983. Conditions of riebeckite formation in the iron-formation

of the Dales Gorge Member, Hamersley Group, Western Australia. American

Mineralogist, 68 (5-6):517.

Moon, D.H., D. Dermatas, and N. Menounou. 2004. Arsenic immobilization by calcium-

arsenic precipitates in lime treated soils. Science of the Total Environment, 330

(1-3):171-185.

NAS. 1977. Arsenic - medical and biological effects of environmental pollutants.

Washington, DC: The National Research Council, National Academy of Sciences.

Nazari, A., A. Bagheri, and S. Riahi. 2011. Properties of geopolmer with seeded fly ash

and rice husk bark ash. Materials Science and Engineering A, - Article In press.

Nordtest. 1995. NT ENVIR 003 - Solid waste, granular inorganic material : Availability

test, Nordtest, Espoo, Finland.

OEWRI. 2008. Standard operating procedure for: LS 13 320 laser diffraction particle size

analyzer operation, Missouri State University and Ozarks Environmental and

Water Resources Institute (OEWRI), Springfield, MO.

Ogunro, V., and O. Sanusi. 2010. Short-term mobility of elements from fly ash based

geopolymer paste. 11th International symposium on environmental geotechnology

and sustainable development (ISEG 2010), Beijing, China,

144

Pacheco-Torgal, F., J. Castro-Gomes, and S. Jalali. 2008a. Alkali-activated binders: A

review. Part 2. About materials and binders manufacture. Construction & building

materials., 22 (7):1315-1322.

Pacheco-Torgal, F., J. Castro-Gomes, and S. Jalali. 2008b. Alkali-activated binders: A

review:Part 1. Historical background, terminology, reaction mechanisms and

hydration products. Construction and Building Materials, 22 (7):1305-1314.

Panagiotopoulou, C., E. Kontori, T. Perraki, and G. Kakali. 2007. Dissolution of

aluminosilicate minerals and by-products in alkaline media. Journal of Materials

Science, 42 (9):2967-2973.

Paoletti, F. 2002. Behavior of oxyanions forming heavy metals in municipal solid waste

incineration. PhD dissertation, Institute for Technical Chemistry (Institut für

Technische Chemie), Karlsruhe Institute of Technology (KIT) formerly

Forschungszentrum Karlsruhe, Karlsruhe, Germany.

Pariatamby, A., C. Subramaniam, S. Mizutani, and H. Takatsuki. 2006. Solidification and

stabilization of fly ash from mixed hazardous waste incinerator using ordinary

Portland cement. Environmental Sciences, 13:8-13.

Parkhurst, D.L., and C.A.J. Appelo. 1999. User's guide to PHREEQC (Version 2): A

computer program for speciation, batch-reaction, one-dimensional transport, and

inverse geochemical calculations. Denver, Colorado: United States Geological

Survey.

PCA. Concrete technology - what causes efflorescence and how can it be avoided?

Portland Cement Asssociation (PCA) 2012. Available from

http://www.cement.org/tech/faq_efflorescence.asp.

Perera, D.S., O. Uchida, E.R. Vance, and K.S. Finnie. 2007. Influence of curing schedule

on the integrity of geopolymers. Journal of Materials Science, 42 (9):3099-3106.

Provis, J.L., P. Duxson, R.M. Harrex, C.-Z. Yong, and J.S.J. van Deventer. 2009.

Valorisation of fly ashes by geopolymerisation. Global NEST Journal, 11 (2):147-

154.

Provis, J.L., and J. van Deventer. 2009. Introduction to geopolymers. In Geopolymers:

Structure, Processing, Properties and Industrial Applications, edited by J. L.

Provis and J. S. J. van Deventer. Cambridge, United Kingdom: Woodhead Publ.

Limited.

Quiroga, P.N., and D.W. Fowler. 2004. The effects of aggregates characteristics on the

performance of Portland cement concrete. Austin, TX: International Center for

Aggregates Research, University of Texas at Austin.

http://www.cement.org/tech/faq_efflorescence.asp

145

Rangan, B.V. 2008. Low calcium fly ash based geopolymer concrete. In Concrete

Construction Engineering Handbook, edited by E. G. Nawy. Boca Raton, Florida:

Taylor & Francis Ltd.

Rangan, B.V. 2009. Engineering properties of geopolymer concrete. In Geopolymers:

structure, processing , properties and industrial applications, edited by J. L. Provis

and J. S. J. Van Deventer. Cambridge, United Kingdom.

Rattanasak, U., and P. Chindaprasirt. 2009. Influence of NaOH solution on the synthesis

of fly ash geopolymer. Minerals Engineering, 22 (12):1073-1078.

Roy, D.M. 1999. Alkali-activated cements opportunities and challenges. Cement and


Saikia, N., S. Kato, and T. Kojima. 2006. Behavior of B, Cr, Se, As, Pb, Cd, and Mo

present in waste leachates generated from combustion residues during the

formation of ettringite. Environmental Toxicology and Chemistry, 25 (7):1710-

1719.

Sakulich, A.R. 2009. Characterization of environmentally-friendly alkali activated slag

cements and ancient building materials. PhD dissertation, Drexel University,

Philadelphia, PA.

Sanusi, O., and V. Ogunro. 2009. Assessment of oxyanions trace elements leaching from

fly ash-based geopolymer. 10th International Symposium on Environmental

Geotechnology and Sustainable Development, Bochum, Germany,

Sanusi, O., and V. Ogunro. 2011a. Influence of calcium on strength and mobility of

elements from monolithic fly ash based geopolymer paste - submitted manuscript,

University of North Carolina at Charlotte.

Sanusi, O., and V. Ogunro. 2011b. Predicting the leaching of oxyanion forming trace

elements from fly ash based geopolymer paste using the availability test -

unpublished manuscript, University of North Carolina at Charlotte.

Sanusi, O., B. Tempest, and V.O. Ogunro. 2011. Mitigating leachability from fly ash

based geopolymer concrete using recycled concrete aggregate (RCA).

Geotechnical special publication of American Society of Civil Engineers, 2

(211):1315-1324.

Schiopu, N., L. Tiruta-Barna, E. Jayr, J. Méhu, and P. Moszkowicz. 2009. Modelling and

simulation of concrete leaching under outdoor exposure conditions. Science of the

Total Environment, 407 (5):1613-1630.

Schuwirth, N., and T. Hofmann. 2006. Comparability of and alternatives to leaching tests

for the assessment of the emission of inorganic soil contamination Journal of Soils

and Sediments, 6 (2):102-112.

146

Schwantes, J.M., and B. Batchelor. 2006. Simulated infinite-dilution leach test.

Environmental Engineering Science, 23 (1):4-13.

Sear, L.K.A. 2001. Properties and use of coal fly ash : a valuable industrial by-product.

London: Thomas Telford.

Shtiza, A., R. Swennen, V. Cappuyns, and A. Tashko. 2009. ANC, BNC and

mobilization of Cr from polluted sediments in function of pH changes.

Environmental Geology, 56 (8):1663-1678.

Škvára, F. 2007. Alkali activated materials or geopolymers? Ceramics- Silikáty, 51

(3):173-177.

Soco, E., and J. Kalembkiewicz. 2009. Investigations on Cr mobility from coal fly ash.

Fuel, 88 (8):1513-1519.

Somna, K., C. Jaturapitakkul, P. Kajitvichyanukul, and P. Chindaprasirt. 2011. NaOH-

activated ground fly ash geopolymer cured at ambient temperature. Fuel, 90

(6):2118-2124.

Struble, L., and J. Godfrey. 2004. How sustainable is concrete? Proceedings of the

International Workshop on Sustainable Development and Concrete Technology

Beijing, China,

Subaer. 2004. Influence of aggregate on the microstructure of geopolymer. PhD

Dissertation, Deparment of Applied Physics, Curtin University of Technology,

Perth, Western Australia.

Sun, P. 2005. Fly ash based inorganic polymeric building material. PhD Dissertation,

Civil Engineering, Wayne State University, Detroit, Michigan.

Suzuki, M., and D. Rohde. 2008. Resolving overlapping peak problems with NORAN

system 7 spectral imaging software, Thermo Fisher scientific, Madison, WI.

Tempest, B. 2010. Engineering characterization of waste derived geopolymer cement

concrete for structural applications. Ph.D Dissertation, Infrastructure and

Environmental Systems, The University of North Carolina at Charlotte, Charlotte,

North Carolina.

Temuujin, J., A. van Riessen, and R. Williams. 2009. Influence of calcium compounds on

the mechanical properties of fly ash geopolymer pastes. Journal of Hazardous

materials, 167 (1-3):82-88.

USEPA. 1986. Method 1320 - Multiple extraction procedure (MEP), United States

Environmental Protection Agency.

USEPA. 1994. Method 1312 - Synthetic precipitation leaching procedure (SPLP), United

States Environmental Protection Agency.

147

USEPA. 2009a. National primary drinking water regulations, United States


USEPA. 2009b. Preliminary method 1313 - Liquid - solid partitioning as a function of

extract pH for constituents in solid materials using a parallel batch extraction,

United States Environmental Protection Agency.

USEPA. 2009c. Preliminary method 1315 - Mass transfer in monolithic or compacted

granular materials using a semi-dynamic leaching procedure, United States


USEPA. 2012. Regional screening table -user's guide 2012 [cited 30th October 2012].

Available from http://www.epa.gov/reg3hwmd/risk/human/rb-

concentration_table/usersguide.htm.

USGS. 2012. Change in nitric acid preservative for trace element samples. United States

Geological Survey (USGS) 1998 [cited 19th July 2012]. Available from

http://water.usgs.gov/admin/memo/QW/qw98.06.html.

Van der Sloot, H., and D. Kosson. 2003. A unified approach for the judgement of

environmental properties of construction materials (cement-based, asphaltic,

unbound aggregates, soil) in different stages of their life cycle. WASCON 2003

conference, San Sebastian, Spain,

Van Jaarsveld, J., and J. Van Deventer. 1999. The effect of metal contaminants on the

formation and properties of waste-based geopolymers. Cement and Concrete

Research, 29 (8):1189-1200.

van Oss, H., and A.C. Padovani. 2002. Cement manufacture and the environment, part I:

chemistry and technology. Journal of Industrial Ecology, 6 (1):89-105.

van Oss, H.G., and A.C. Padovani. 2003. Cement manufacture and the environment, part

II: environmental challenges and opportunities. Journal of Industrial Ecology, 7

(1):93-126.

Wang, T. 2007. The leaching behavior of arsenic, selenium and other trace elements in

coal fly ash. PhD dissertation, Civil Engineering, University of Missouri-Rolla,

Rolla, Missouri.

Wang, T., T. Su, J. Wang, and K. Ladwig. 2007. Calcium effect on asernic (v) adsorption

onto coal fly ash. World of Coal Ash conference (WOCA 2007), Lexington,

Kentucky,

Xu, H., and J.S.J. Van Deventer. 2000. The geopolymerisation of alumino-silicate

minerals. International Journal of Mineral Processing, 59 (3):247-266.

http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/usersguide.htm

http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/usersguide.htm

http://water.usgs.gov/admin/memo/QW/qw98.06.html

148

Xu, J., Y. Zhou, Q. Chang, and H. Qu. 2006. Study on the factors of affecting the

immobilization of heavy metals in fly ash-based geopolymers. Materials Letters,

60 (6):820-822.

Yao, X., Z. Zhang, H. Zhu, and Y. Chen. 2009. Geopolymerization process of alkali-

metakaolinite characterized by isothermal calorimetry. Thermochimica Acta, 493

(1-2):49-54.

Yip, C., G. Lukey, and J. Van Deventer. 2005. The coexistence of geopolymeric gel and

calcium silicate hydrate at the early stage of alkaline activation. Cement and


Yip, C., and J. van Deventer. 2003. Microanalysis of calcium silicate hydrate gel formed

within a geopolymeric binder. Journal of Materials Science, 38 (18):3851-3860.

Zhang, J., J.L. Provis, D. Feng, and J.S. van Deventer. 2008. Geopolymers for

immobilization of Cr(6+), Cd(2+), and Pb(2+). Journal of Hazardous materials,

157 (2-3):2-3.

Zhang, M. 2000. Incorporation of oxyanionic boron, chromium, molybdenum, and

selenium into hydrocalumite and ettringite: Application to cementitious systems.

PhD dissertation, Earth Science, Waterloo, Ontario, CanadaUniversity of

Waterloo.

Zhang, M., and E.J. Reardon. 2003. Removal of B, Cr, Mo, and Se from wastewater by

incorporation into hydrocalumite and ettringite. Environmental science &

technology, 37 (13):2947-2952.

Zhang, M., and E.J. Reardon. 2005. Chromate and selenate hydrocalumite solid solutions

and their applications in waste treatment. Science in China Series C: Life

Sciences, 48:165-173.

Zhang, Y., W. Sun, and Z. Li. 2009. Preparation and microstructure characterization of

poly-sialate-disiloxo type of geopolymeric cement. Journal of Central South

University of Technology, 16 (6):906-913.

Zheng, L., C. Wang, W. Wang, Y. Shi, and X. Gao. 2011. Immobilization of MSWI fly

ash through geopolymerization: Effects of water-wash. Waste Management, 31

(2):311-317.

Zhu, C. 2009. Geochemical modeling of reaction paths and geochemical reaction

networks. Reviews in Mineralogy and Geochemistry, 70 (1):533.

Zhu, C., and G.M. Anderson. 2002. Environmental applications of geochemical

modeling. Cambridge, United Kingdom: Cambridge University Press.

149

Zhu, Y.N., X.H. Zhang, Q.L. Xie, D.Q. Wang, and G.W. Cheng. 2006. Solubility and

stability of calcium arsenates at 25 C. Water, Air, & Soil Pollution, 169 (1):221-

238.

150

APPENDIX A: MIX DESIGN FOR THE GEOPOLYMER CONCRETE

TABLE A-1: Mix design for the geopolymer concrete (kg/m3)

Mix HL( %) HL (kg) CFA(kg) FA (kg) CA (kg) SF (kg) NaOH (kg) H2O (kg) w/c

GPC 0.000 0.000 483.437 773.371 774.012 36.202 48.376 206.959 0.364

GP1 0.530 2.563 483.437 773.371 774.012 36.202 48.376 206.959 0.363

GP2 0.994 4.806 483.437 773.371 774.012 36.202 48.376 206.959 0.361

GP3 1.988 9.611 483.437 773.371 774.012 36.202 48.376 206.959 0.358

TABLE A-2: Percentage of each component in the geopolymer concrete (%)

Aggregates* CFA SF HL NaOH H2O Total

67 20.8 1.6 0.0 2.1 8.9 100.0

67 20.8 1.6 0.1 2.1 8.9 100.0

66 20.8 1.6 0.2 2.1 8.9 100.0

66 20.7 1.6 0.4 2.1 8.9 100.0

*Aggregates = FA + CA

TABLE A-3: Explanation of notations used in mix design

HL Hydrated lime

CFA Coal fly ash

FA Fine agregate

CA Coarse aggregate

SF Silica fume

NaOH Sodium hydroxide

H2O water

151

APPENDIX B: COMPRESSIVE STRENGTH MEASUREMENTS FOR THE

GEOPOLYMER CONCRETE MIXES

TABLE B-1: Compressive strength of the geopolymer concrete (psi)

7d_wo* 28d_wo 7d_w** 28d_w

GPC 951.9 3155.772 7542.79 7811.404

GPC 974.11 3121.392 7472.34 8330.362

GPC 973.26 1664.686 5344.46 8209.819

GP1 1008.065 1898.557 5286.786 5894.171

GP1 1050.792 2065.507 5563.667 5768.251

GP1 1075.41 1950.764 5440.719 6377.9

GP2 1194.963 1968.874 6530.702 7520.939

GP2 1177.985 2246.604 6264.431 7231.749

GP2 1211.658 2146.576 6363.894 7209.536

GP3 1378.183 1867.148 6579.938 7066.638

GP3 1437.323 1942.841 5539.191 6934.776

GP3 1182.654 2000.849 6218.308 4607.668

TABLE B-2: Compressive strength of geopolymer

concrete (MPa)

7d_wo* 28d_wo 7d_w** 28d_w

GPC 6.56 21.76 52.01 53.86

GPC 6.72 21.52 51.51 57.43

GPC 6.71 11.48 36.85 56.61

GP1 6.95 13.09 36.45 40.64

GP1 7.25 14.25 38.36 39.77

GP1 7.41 13.45 37.51 43.97

GP2 8.24 13.58 45.03 51.86

GP2 8.12 15.49 43.19 49.86

GP2 8.36 14.8 43.88 49.7

GP3 9.5 12.87 45.37 48.72

GP3 9.91 13.4 38.19 47.82

GP3 8.16 13.8 42.87 31.77

*Geopolymer concrete cured without heat

**Geopolymer concrete cured at 75oC

152

APPENDIX C: STATISTICAL ANALYSIS OF THE GEOPOLYMER CONCRETE

COMPRESSIVE STRENGTH

APPENDIX C1: 7 DAYS COMPRRESIVE STRENGTH FOR GEOPOLYMER

CONCRETE CURED WITHOUT HEAT

Strength_7d_wo

153

154


CONCRETE CURED WITHOUT HEAT

Strength_28d_wo

155

156


CONCRETE CURED WITH HEAT

Strength_7d_w

157

158


CONCRETE CURED WITH HEAT

Strength_28d_w

.

159

160

APPENDIX D: PH DEPENDENCE LEACHING TEST RESULTS FOR OTHER

ELEMENTS

FIGURE D-1: pH dependence mobility of elements from CFA and SF

161

FIGURE D-2: pH dependence mobility of elements from CFA and SF

162

FIGURE D-3: pH dependence mobility of Mo and V from the CFA and SF

FIGURE D-4: pH dependence mobility of Mo and V from the geopolymer concretes

163

FIGURE D-5: pH dependence mobility of elements from the geopolymer concretes

164

FIGURE D-6: pH dependence mobility of elements from the geopolymer concretes

165

APPENDIX E: ENLARGED CUMULATIVE PLOT OF THE ELEMENTS

FIGURE E-1: Plot showing enlarged cumulative release of As

FIGURE E-2: Plot showing enlarged cumulative release of Se

166

FIGURE E-3: Plot showing enlarged cumulative release of Cr

167

APPENDIX F: INPUT FILE FOR PHREEQC/PHREEPLOT

Input file – GPC composition used in this file

SPECIATION

jobTitle "Speciation of oxyanion forming elements (As, Cr, amd Se) vs pH"

database llnl.dat # this is a larger database (750kB) contains over 1155 minerals

calculationType species # plot %C species vs pH

calculationMethod 1 # Full set of speciation calculation done

mainSpecies As Cr Se # produce species plot for these elements

xmin 1 # controls the range of pH plotted - min pH

xmax 13 # max pH

resolution 120 # (13-1)/120 = 0.1 pH division

debug 2 #create the phreeqcall.out that conatisn the accumulated phreeqc.out

PLOT

plotTitle "Speciation of oxyanion forming elements"

xtitle pH

ytitle " % species"

multipageFile True # put all the plots into a single file

CHEMISTRY

# first simulation - initial solution calculation only calculated once

# speciation modeling section -osanusi

include 'speciesvspht.inc' # calculates % species and plot it against the pH

PRINT

-reset true # Output initial solution calculation

-equilibrium_phases true # output the equilibrium phases

-species TRUE #output the species

SELECTED_OUTPUT

reset false

high_precision true

PHASES # temporarily add this to the database

Fix_H+

H+ = H+

log_K 0.0

CaSeO3:2H2O

CaSeO3:2H2O = + 1.0000 Ca++ + 1.0000 SeO3-- + 2.0000 H2O

log_k -4.6213

-delta_H -14.1963 kJ/mol # Calculated enthalpy of reaction

CaSeO3:2H2O # Enthalpy of formation: -384.741 kcal/mol

-analytic -4.1771e+001 -2.0735e-002 9.7870e+002 1.6180e+001 1.6634e+00

# -Range: 0-200

CaSeO3:H2O # Cornelis et al. 2008

CaSeO3:H2O = + 1.0000 Ca++ + 1.0000 SeO3-- + 1.0000 H2O

log_k -6.84

CaSeO4

CaSeO4 = + 1.0000 Ca++ + 1.0000 SeO4--

log_k -3.0900

-delta_H 0 # Not possible to calculate enthalpy of reaction

CaSeO4 # Enthalpy of formation: 0 kcal/mol

Ca3(AsO4)2:3H2O #Cornelis et al 2008

Ca3(AsO4)2:3H2O = + 3.0000 Ca+2 + 2.000 AsO4-3 + 3.0000 H2O

log_k -21.14

CaHAsO4 #Weilite source: Alexandratos et al. 2007

CaHAsO4 = +1.0000Ca++ +1.0000HAsO4--

log_k -2.66

CaHAsO4:H2O #Haidingerite source: Alexandratos et al. 2007

CaHAsO4:H2O = +1.0000Ca++ +1.0000HAsO4-- +1.0000H2O

168

log_k -4.79

CaCrO4 # from sit.dat

CaCrO4 = +1.000Ca+2 +1.000CrO4-2

log_k -3.15 #03DEA

delta_h -22.814 kJ/mol #

# Enthalpy of formation: -1399.186 kJ/mol

Ca3(AsO4)2:10H2O #Phaunouvite source:Cornelis etal. 2008

Ca3(AsO4)2:10H2O = +3.0000Ca++ +2.0000AsO4--- +10.0000H2O

log_k -21.21

Ca5(AsO4)3(OH)

Ca5(AsO4)3(OH) = +5.0000Ca++ +3.0000AsO4--- +1.0000OH-

log_k -40.12

Cr-ettringite # from sit.dat

Ca6(Al(OH)6)2(CrO4)3:26H2O = +6.000Ca+2 +2.000Al+3 -12.000H+ +3.000CrO4-2

+38.000H2O

log_k 60.28 #00PER/PAL

delta_h -509.59 kJ/mol #00PER/PAL


Se-ettringite # Chrysochoou and Dermatas 2006

Ca6(Al(OH)6)2(SeO4)3:31.5H2O = +6.000Ca+2 +2.000Al+3 +3.000SeO4-2 -12.000H+ +43.500H2O

log_k 61.29

Se-monosulfoaluminate # Cornelis et al 2008

Ca4(Al(OH)6)2SeO4:9H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000SeO4-2 +21.000H2O

log_k 73.40

Monosulfoaluminate # Cornelis et al. 2008

Ca4Al2(SO4)(OH)12:13H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000SO4-2

+25.000H2O

log_k 72.57 #07BLA/BOU


# Enthalpy of formation: -8780.45 kJ/mol 82WAG/EVA

Cr-monosulfoaluminate #Cornelis et al. 2008

Ca4Al2(OH)12(CrO4):9H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000CrO4-2

+21.000H2O

log_k 71.36 #01PER/PAL

delta_h -545.98 kJ/mol #01PER/PAL


#CSH1.6 # from sit.dat

#Ca1.6SiO3.6:2.58H2O = +1.600Ca+2 -3.200H+ +1.000H4(SiO4) +2.180H2O

# log_k -28 #07BLA/BOU

# delta_h -133.314 kJ/mol #

# Enthalpy of formation: -2819.79 kJ/mol 07BLA/BOU

#CSH1.2 # sit.dat


# log_k -19.3 #07BLA/BOU



#CSH0.8 #sit.dat


# log_k -11.05 #07BLA/BOU



CaSeO4:2H2O # from sit.dat

CaSeO4:2H2O = +1.000Ca+2 +1.000SeO4-2 +2.000H2O

log_k -2.68 #05OLI/NOL


# Enthalpy of formation: -1709 kJ/mol 05OLI/NOL

169

# The concentration measured from the WLT was used as solution composition

SOLUTION 1 # Composition of the aqueous solution obtained from the tests

temp 25 # Temperature in C

pH 11.23 # Material ph or pH at zero acid and base addition

units mg/L

density 0.997 #kg/l

Na 564.50

Si 160.00

V 1.685

Al 0.4485

As 1.0231

B 1.78

Ca 0.644

Fe 0.329 # total Fe

Mg 0.164

Mo 0.265

Se 0.405

Cr 0.025

Cl 1.20 Charge

F 0.395

N(5) 0.195

P 31.50

S(6) 155.00

# no reaction so no need to SAVE solution 1

END

# second (final) simulation - the final simulation is iterated many times as required by

the speciation procedure

# batch reaction modeling - osanusi

USE solution 1

EQUILIBRIUM_PHASES 1

Fix_H+ -<x_axis> NaOH

-force_equality true

Halite -12 10 # maintains Na in the system for functioning of fix_H+ when

it goes -ve

# Include possible As, Cr and Se solubility controlling minerals

Cr-ettringite 0.5 0

Se-ettringite 0.5 0

Cr-monosulfoaluminate 0.5 0

Se-monosulfoaluminate 0.5 0

CaHAsO4 0.5 0

Ettringite 0.0 0

Monosulfoaluminate 0.0 0

CaHAsO4:H2O 0.5 0

Ca3(AsO4)2:10H2O 0.5 0

Ca5(AsO4)3(OH) 0.5 0

CaSeO4 0.5 0

CaSeO4:2H2O 0.5 0

Ca3(AsO4)2:10H2O 0.5 0

CaSeO3:2H2O 0.5 0

CaCrO4 0.5 0

END

170

APPENDIX G: OUTPUT FILE FOR PHREEQC/PHREEPLOT

Output file – obtained from simulation performed using GPC composition

------------------------------------

Reading input data for simulation 1.

------------------------------------

PRINT

reset false

equilibrium_phases true

species TRUE

SELECTED_OUTPUT

reset false

high_precision true

PHASES

Fix_H+

H+ = H+

log_K 0.0

CaSeO3:2H2O

CaSeO3:2H2O = + 1.0000 Ca++ + 1.0000 SeO3-- + 2.0000 H2O

log_k -4.6213

delta_h -14.1963 kJ/mol

analytical_expression -4.1771e+001 -2.0735e-002 9.7870e+002 1.6180e+001

1.6634e+001

CaSeO3:H2O

CaSeO3:H2O = + 1.0000 Ca++ + 1.0000 SeO3-- + 1.0000 H2O

log_k -6.84

CaSeO4

CaSeO4 = + 1.0000 Ca++ + 1.0000 SeO4--

log_k -3.0900

delta_h 0

Ca3(AsO4)2:3H2O

Ca3(AsO4)2:3H2O = + 3.0000 Ca+2 + 2.000 AsO4-3 + 3.0000 H2O

log_k -21.14

CaHAsO4

CaHAsO4 = +1.0000Ca++ +1.0000HAsO4--

log_k -2.66

CaHAsO4:H2O

CaHAsO4:H2O = +1.0000Ca++ +1.0000HAsO4-- +1.0000H2O

log_k -4.79

CaCrO4

CaCrO4 = +1.000Ca+2 +1.000CrO4-2

log_k -3.15


Ca3(AsO4)2:10H2O

Ca3(AsO4)2:10H2O = +3.0000Ca++ +2.0000AsO4--- +10.0000H2O

log_k -21.21

Ca5(AsO4)3(OH)

Ca5(AsO4)3(OH) = +5.0000Ca++ +3.0000AsO4--- +1.0000OH-

log_k -40.12

Cr-ettringite

Ca6(Al(OH)6)2(CrO4)3:26H2O = +6.000Ca+2 +2.000Al+3 -12.000H+

+3.000CrO4-2 +38.000H2O

log_k 60.28


Se-ettringite

Ca6(Al(OH)6)2(SeO4)3:31.5H2O = +6.000Ca+2 +2.000Al+3 +3.000SeO4-2 -12.000H+

+43.500H2O

log_k 61.29

Se-monosulfoaluminate

Ca4(Al(OH)6)2SeO4:9H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000SeO4-2 +21.000H2O

log_k 73.40

Monosulfoaluminate

171

Ca4Al2(SO4)(OH)12:13H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000SO4-2

+25.000H2O

log_k 72.57


Cr-monosulfoaluminate

Ca4Al2(OH)12(CrO4):9H2O = +4.000Ca+2 +2.000Al+3 -12.000H+ +1.000CrO4-2

+21.000H2O

log_k 71.36


CaSeO4:2H2O

CaSeO4:2H2O = +1.000Ca+2 +1.000SeO4-2 +2.000H2O

log_k -2.68


SOLUTION 1

temp 25

pH 11.23

units mg/L

density 0.997

Na 564.50

Si 160.00

V 1.685

Al 0.4485

As 1.0231

B 1.78

Ca 0.644

Fe 0.329

Mg 0.164

Mo 0.265

Se 0.405

Cr 0.025

Cl 1.20 Charge

F 0.395

N(5) 0.195

P 31.50

S(6) 155.00

END

-------------------------------------------

Beginning of initial solution calculations.

-------------------------------------------

Initial solution 1.

WARNING: USER_PUNCH: Headings count doesn't match number of calls to PUNCH.

-----------------------------Solution composition------------------------------

Elements Molality Moles

Al 1.669e-005 1.669e-005

As 1.371e-005 1.371e-005

B 1.653e-004 1.653e-004

Ca 1.613e-005 1.613e-005

Cl 1.437e-002 1.437e-002 Charge balance

Cr 2.164e-007 2.164e-007

F 2.087e-005 2.087e-005

Fe 5.914e-006 5.914e-006

Mg 6.774e-006 6.774e-006

Mo 2.773e-006 2.773e-006

N(5) 1.398e-005 1.398e-005

Na 2.465e-002 2.465e-002

P 1.021e-003 1.021e-003

S(6) 1.620e-003 1.620e-003

Se 5.149e-006 5.149e-006

Si 2.674e-003 2.674e-003

V 3.321e-005 3.321e-005

----------------------------Description of solution----------------------------

pH = 11.230

pe = 4.000

172

Activity of water = 0.999

Ionic strength = 2.602e-002

Mass of water (kg) = 1.000e+000

Total alkalinity (eq/kg) = 7.107e-003

Total carbon (mol/kg) = 0.000e+000

Total CO2 (mol/kg) = 0.000e+000

Temperature (deg C) = 25.000

Electrical balance (eq) = 1.261e-018

Percent error, 100*(Cat-|An|)/(Cat+|An|) = 0.00

Iterations = 50

Total H = 1.110562e+002

Total O = 5.554645e+001

----------------------------Distribution of species----------------------------

Log Log Log

Species Molality Activity Molality Activity Gamma

OH- 1.914e-003 1.635e-003 -2.718 -2.786 -0.069

H+ 6.680e-012 5.888e-012 -11.175 -11.230 -0.055

H2O 5.553e+001 9.992e-001 1.744 -0.000 0.000

Al 1.669e-005

AlO2- 1.663e-005 1.426e-005 -4.779 -4.846 -0.067

NaAlO2 5.418e-008 5.418e-008 -7.266 -7.266 0.000

HAlO2 2.451e-010 2.451e-010 -9.611 -9.611 0.000

Al(OH)2+ 1.157e-015 9.915e-016 -14.937 -15.004 -0.067

AlOH+2 4.635e-021 2.516e-021 -20.334 -20.599 -0.265

AlHPO4+ 1.631e-023 1.398e-023 -22.788 -22.855 -0.067

AlF2+ 2.293e-025 1.965e-025 -24.640 -24.707 -0.067

AlF+2 1.489e-025 8.084e-026 -24.827 -25.092 -0.265

AlF3 1.511e-026 1.511e-026 -25.821 -25.821 0.000

Al+3 4.200e-027 1.324e-027 -26.377 -26.878 -0.501

AlSO4+ 1.267e-027 1.086e-027 -26.897 -26.964 -0.067

Al(SO4)2- 7.888e-029 6.760e-029 -28.103 -28.170 -0.067

AlF4- 2.705e-029 2.318e-029 -28.568 -28.635 -0.067

Al2(OH)2+4 1.080e-038 1.030e-039 -37.967 -38.987 -1.021

AlH2PO4+2 7.599e-039 4.125e-039 -38.119 -38.385 -0.265

Al3(OH)4+5 0.000e+000 0.000e+000 -48.033 -49.596 -1.563

Al13O4(OH)24+7 0.000e+000 0.000e+000 -85.731 -88.796 -3.065

As(-3) 0.000e+000

AsH3 0.000e+000 0.000e+000 -156.444 -156.444 0.000

As(3) 0.000e+000

AsO2OH-2 0.000e+000 0.000e+000 -57.669 -57.940 -0.271

H2AsO3- 0.000e+000 0.000e+000 -58.093 -58.160 -0.067

AsO2- 0.000e+000 0.000e+000 -58.112 -58.179 -0.067

HAsO2 0.000e+000 0.000e+000 -60.117 -60.117 0.000

As(OH)3 0.000e+000 0.000e+000 -60.176 -60.176 0.000

As(5) 1.371e-005

AsO3F-2 1.371e-005 7.343e-006 -4.863 -5.134 -0.271

HAsO3F- 3.746e-011 3.210e-011 -10.426 -10.493 -0.067

HAsO4-2 3.596e-036 1.926e-036 -35.444 -35.715 -0.271

AsO4-3 3.430e-036 8.392e-037 -35.465 -36.076 -0.611

H2AsO4- 0.000e+000 0.000e+000 -40.098 -40.165 -0.067

H3AsO4 0.000e+000 0.000e+000 -49.150 -49.150 0.000

B(-5) 0.000e+000

BH4- 0.000e+000 0.000e+000 -181.463 -181.530 -0.067

B(3) 1.653e-004

BO2- 1.585e-004 1.358e-004 -3.800 -3.867 -0.067

NaB(OH)4 5.349e-006 5.349e-006 -5.272 -5.272 0.000

B(OH)3 1.490e-006 1.490e-006 -5.827 -5.827 0.000

CaB(OH)4+ 1.543e-009 1.323e-009 -8.812 -8.879 -0.067

MgB(OH)4+ 5.752e-010 4.930e-010 -9.240 -9.307 -0.067

B2O(OH)5- 9.086e-020 7.787e-020 -19.042 -19.109 -0.067

BF2(OH)2- 1.584e-021 1.357e-021 -20.800 -20.867 -0.067

BF3OH- 2.431e-031 2.084e-031 -30.614 -30.681 -0.067

BF4- 0.000e+000 0.000e+000 -42.237 -42.304 -0.067

Ca 1.613e-005

CaPO4- 1.583e-005 1.357e-005 -4.800 -4.867 -0.067

Ca+2 2.454e-007 1.383e-007 -6.610 -6.859 -0.249

CaHPO4 3.194e-008 3.194e-008 -7.496 -7.496 0.000

CaSO4 1.620e-008 1.620e-008 -7.791 -7.791 0.000

173

CaOH+ 3.867e-009 3.314e-009 -8.413 -8.480 -0.067

CaB(OH)4+ 1.543e-009 1.323e-009 -8.812 -8.879 -0.067

CaCl+ 4.170e-010 3.574e-010 -9.380 -9.447 -0.067

CaP2O7-2 5.166e-011 2.767e-011 -10.287 -10.558 -0.271

CaNO3+ 9.616e-012 8.242e-012 -11.017 -11.084 -0.067

CaCl2 5.126e-012 5.126e-012 -11.290 -11.290 0.000

CaF+ 5.008e-012 4.292e-012 -11.300 -11.367 -0.067

CaH2PO4+ 1.003e-020 8.597e-021 -19.999 -20.066 -0.067

Cl(-1) 1.437e-002

Cl- 1.433e-002 1.220e-002 -1.844 -1.914 -0.070

NaCl 4.270e-005 4.270e-005 -4.370 -4.370 0.000

MgCl+ 4.812e-010 4.124e-010 -9.318 -9.385 -0.067

CaCl+ 4.170e-010 3.574e-010 -9.380 -9.447 -0.067

CaCl2 5.126e-012 5.126e-012 -11.290 -11.290 0.000

HCl 1.613e-014 1.613e-014 -13.792 -13.792 0.000

FeCl+ 2.579e-022 2.211e-022 -21.589 -21.655 -0.067

CrO3Cl- 2.199e-024 1.884e-024 -23.658 -23.725 -0.067

FeCl2 1.447e-026 1.447e-026 -25.840 -25.840 0.000

FeCl4-2 1.161e-029 6.217e-030 -28.935 -29.206 -0.271

FeCl2+ 5.584e-031 4.786e-031 -30.253 -30.320 -0.067

FeCl+2 8.930e-032 4.848e-032 -31.049 -31.314 -0.265

FeCl4- 9.985e-038 8.558e-038 -37.001 -37.068 -0.067

CrCl+2 2.229e-038 1.210e-038 -37.652 -37.917 -0.265

CrCl2+ 3.786e-040 3.245e-040 -39.422 -39.489 -0.067

Cl(1) 3.195e-030

ClO- 3.194e-030 2.738e-030 -29.496 -29.563 -0.067

HClO 5.978e-034 5.978e-034 -33.223 -33.223 0.000

Cl(3) 0.000e+000

ClO2- 0.000e+000 0.000e+000 -50.039 -50.106 -0.067

HClO2 0.000e+000 0.000e+000 -58.166 -58.166 0.000

Cl(5) 0.000e+000

ClO3- 0.000e+000 0.000e+000 -56.729 -56.797 -0.069

Cl(7) 0.000e+000

ClO4- 0.000e+000 0.000e+000 -67.722 -67.790 -0.069

Cr(2) 0.000e+000

Cr+2 0.000e+000 0.000e+000 -48.108 -48.373 -0.265

Cr(3) 5.454e-019

Cr(OH)4- 5.386e-019 4.616e-019 -18.269 -18.336 -0.067

Cr(OH)3 6.833e-021 6.833e-021 -20.165 -20.165 0.000

Cr(OH)2+ 9.374e-024 8.034e-024 -23.028 -23.095 -0.067

CrOH+2 4.371e-029 2.373e-029 -28.359 -28.625 -0.265

Cr+3 4.437e-036 1.398e-036 -35.353 -35.854 -0.501

CrCl+2 2.229e-038 1.210e-038 -37.652 -37.917 -0.265

CrCl2+ 3.786e-040 3.245e-040 -39.422 -39.489 -0.067

Cr2(OH)2+4 0.000e+000 0.000e+000 -53.289 -54.309 -1.021

Cr3(OH)4+5 0.000e+000 0.000e+000 -69.231 -70.795 -1.563

Cr(5) 2.502e-009

CrO4-3 2.502e-009 6.123e-010 -8.602 -9.213 -0.611

Cr(6) 2.139e-007

CrO4-2 2.139e-007 1.146e-007 -6.670 -6.941 -0.271

HCrO4- 2.617e-012 2.243e-012 -11.582 -11.649 -0.067

Cr2O7-2 3.139e-022 1.681e-022 -21.503 -21.774 -0.271

CrO3Cl- 2.199e-024 1.884e-024 -23.658 -23.725 -0.067

H2CrO4 6.038e-025 6.038e-025 -24.219 -24.219 0.000

F 2.087e-005

AsO3F-2 1.371e-005 7.343e-006 -4.863 -5.134 -0.271

F- 7.151e-006 6.107e-006 -5.146 -5.214 -0.069

NaF 1.301e-008 1.301e-008 -7.886 -7.886 0.000

HAsO3F- 3.746e-011 3.210e-011 -10.426 -10.493 -0.067

MgF+ 7.449e-012 6.384e-012 -11.128 -11.195 -0.067

CaF+ 5.008e-012 4.292e-012 -11.300 -11.367 -0.067

PO3F-2 4.470e-013 2.394e-013 -12.350 -12.621 -0.271

HF 5.521e-014 5.521e-014 -13.258 -13.258 0.000

HF2- 9.529e-020 8.167e-020 -19.021 -19.088 -0.067

HPO3F- 2.068e-020 1.773e-020 -19.684 -19.751 -0.067

BF2(OH)2- 1.584e-021 1.357e-021 -20.800 -20.867 -0.067

FeF+ 4.062e-024 3.481e-024 -23.391 -23.458 -0.067

AlF2+ 2.293e-025 1.965e-025 -24.640 -24.707 -0.067

AlF+2 1.489e-025 8.084e-026 -24.827 -25.092 -0.265

AlF3 1.511e-026 1.511e-026 -25.821 -25.821 0.000

H2F2 7.580e-027 7.580e-027 -26.120 -26.120 0.000

174

VO2F 6.951e-027 6.951e-027 -26.158 -26.158 0.000

AlF4- 2.705e-029 2.318e-029 -28.568 -28.635 -0.067

VO2F2- 1.428e-029 1.224e-029 -28.845 -28.912 -0.067

FeF+2 4.025e-030 2.185e-030 -29.395 -29.661 -0.265

H2PO3F 6.676e-031 6.676e-031 -30.175 -30.175 0.000

FeF2+ 2.519e-031 2.159e-031 -30.599 -30.666 -0.067

BF3OH- 2.431e-031 2.084e-031 -30.614 -30.681 -0.067

VOF+ 1.033e-035 8.851e-036 -34.986 -35.053 -0.067

VOF2 3.257e-038 3.257e-038 -37.487 -37.487 0.000

BF4- 0.000e+000 0.000e+000 -42.237 -42.304 -0.067

SiF6-2 0.000e+000 0.000e+000 -53.747 -54.018 -0.271

Fe(2) 1.017e-016

FePO4- 8.408e-017 7.206e-017 -16.075 -16.142 -0.067

Fe(OH)3- 1.419e-017 1.216e-017 -16.848 -16.915 -0.067

Fe(OH)2 1.800e-018 1.800e-018 -17.745 -17.745 0.000

FeOH+ 1.558e-018 1.335e-018 -17.807 -17.874 -0.067

Fe+2 4.417e-020 2.488e-020 -19.355 -19.604 -0.249

FeHPO4 4.164e-020 4.164e-020 -19.380 -19.380 0.000

Fe(OH)4-2 3.852e-021 2.063e-021 -20.414 -20.685 -0.271

FeSO4 3.162e-021 3.162e-021 -20.500 -20.500 0.000

FeCl+ 2.579e-022 2.211e-022 -21.589 -21.655 -0.067

FeF+ 4.062e-024 3.481e-024 -23.391 -23.458 -0.067

FeCl2 1.447e-026 1.447e-026 -25.840 -25.840 0.000

FeCl4-2 1.161e-029 6.217e-030 -28.935 -29.206 -0.271

FeH2PO4+ 3.602e-032 3.087e-032 -31.443 -31.510 -0.067

Fe(3) 5.914e-006

Fe(OH)4- 5.798e-006 4.969e-006 -5.237 -5.304 -0.067

Fe(OH)3 1.166e-007 1.166e-007 -6.933 -6.933 0.000

Fe(OH)2+ 1.714e-012 1.469e-012 -11.766 -11.833 -0.067

FeOH+2 4.815e-020 2.614e-020 -19.317 -19.583 -0.265

FeHPO4+ 1.771e-022 1.518e-022 -21.752 -21.819 -0.067

Fe+3 7.570e-029 2.386e-029 -28.121 -28.622 -0.501

FeF+2 4.025e-030 2.185e-030 -29.395 -29.661 -0.265

FeSO4+ 2.159e-030 1.851e-030 -29.666 -29.733 -0.067

FeCl2+ 5.584e-031 4.786e-031 -30.253 -30.320 -0.067

FeF2+ 2.519e-031 2.159e-031 -30.599 -30.666 -0.067

FeCl+2 8.930e-032 4.848e-032 -31.049 -31.314 -0.265

Fe(SO4)2- 2.927e-032 2.509e-032 -31.534 -31.601 -0.067

FeNO3+2 5.227e-033 2.837e-033 -32.282 -32.547 -0.265

Fe2(OH)2+4 1.929e-037 1.839e-038 -36.715 -37.735 -1.021

FeCl4- 9.985e-038 8.558e-038 -37.001 -37.068 -0.067

FeH2PO4+2 1.609e-039 8.735e-040 -38.793 -39.059 -0.265

Fe3(OH)4+5 0.000e+000 0.000e+000 -45.685 -47.249 -1.563

H(0) 5.468e-034

H2 2.734e-034 2.751e-034 -33.563 -33.560 0.003

Mg 6.774e-006

MgPO4- 6.675e-006 5.721e-006 -5.176 -5.243 -0.067

Mg+2 7.366e-008 4.332e-008 -7.133 -7.363 -0.231

MgHPO4 1.480e-008 1.480e-008 -7.830 -7.830 0.000

MgSO4 9.275e-009 9.275e-009 -8.033 -8.033 0.000

MgB(OH)4+ 5.752e-010 4.930e-010 -9.240 -9.307 -0.067

MgCl+ 4.812e-010 4.124e-010 -9.318 -9.385 -0.067

MgP2O7-2 4.793e-011 2.567e-011 -10.319 -10.591 -0.271

MgF+ 7.449e-012 6.384e-012 -11.128 -11.195 -0.067

MgH2PO4+ 5.718e-021 4.901e-021 -20.243 -20.310 -0.067

Mg4(OH)4+4 5.444e-024 5.191e-025 -23.264 -24.285 -1.021

Mo 2.773e-006

MoO4-2 2.773e-006 1.505e-006 -5.557 -5.822 -0.265

N(5) 1.398e-005

NO3- 1.398e-005 1.189e-005 -4.855 -4.925 -0.070

CaNO3+ 9.616e-012 8.242e-012 -11.017 -11.084 -0.067

HNO3 3.663e-018 3.663e-018 -17.436 -17.436 0.000

FeNO3+2 5.227e-033 2.837e-033 -32.282 -32.547 -0.265

Na 2.465e-002

Na+ 2.325e-002 1.992e-002 -1.634 -1.701 -0.067

NaHSiO3 1.147e-003 1.147e-003 -2.940 -2.940 0.000

NaSO4- 1.231e-004 1.055e-004 -3.910 -3.977 -0.067

NaHPO4- 8.128e-005 6.966e-005 -4.090 -4.157 -0.067

NaCl 4.270e-005 4.270e-005 -4.370 -4.370 0.000

NaOH 5.620e-006 5.620e-006 -5.250 -5.250 0.000

NaB(OH)4 5.349e-006 5.349e-006 -5.272 -5.272 0.000

175

NaAlO2 5.418e-008 5.418e-008 -7.266 -7.266 0.000

NaF 1.301e-008 1.301e-008 -7.886 -7.886 0.000

NaP2O7-3 5.036e-010 1.232e-010 -9.298 -9.909 -0.611

Na2P2O7-2 3.641e-010 1.950e-010 -9.439 -9.710 -0.271

NaHP2O7-2 2.741e-013 1.468e-013 -12.562 -12.833 -0.271

O(0) 1.669e-025

O2 8.347e-026 8.400e-026 -25.078 -25.076 0.003

P(-3) 0.000e+000

PH4+ 0.000e+000 0.000e+000 -199.589 -199.656 -0.067

P(5) 1.021e-003

HPO4-2 7.849e-004 4.204e-004 -3.105 -3.376 -0.271

PO4-3 1.322e-004 3.236e-005 -3.879 -4.490 -0.611

NaHPO4- 8.128e-005 6.966e-005 -4.090 -4.157 -0.067

CaPO4- 1.583e-005 1.357e-005 -4.800 -4.867 -0.067

MgPO4- 6.675e-006 5.721e-006 -5.176 -5.243 -0.067

H2PO4- 4.884e-008 4.186e-008 -7.311 -7.378 -0.067

CaHPO4 3.194e-008 3.194e-008 -7.496 -7.496 0.000

MgHPO4 1.480e-008 1.480e-008 -7.830 -7.830 0.000

NaP2O7-3 5.036e-010 1.232e-010 -9.298 -9.909 -0.611

P2O7-4 4.202e-010 3.433e-011 -9.377 -10.464 -1.088

Na2P2O7-2 3.641e-010 1.950e-010 -9.439 -9.710 -0.271

CaP2O7-2 5.166e-011 2.767e-011 -10.287 -10.558 -0.271

MgP2O7-2 4.793e-011 2.567e-011 -10.319 -10.591 -0.271

HP2O7-3 1.349e-012 3.300e-013 -11.870 -12.481 -0.611

PO3F-2 4.470e-013 2.394e-013 -12.350 -12.621 -0.271

NaHP2O7-2 2.741e-013 1.468e-013 -12.562 -12.833 -0.271

FePO4- 8.408e-017 7.206e-017 -16.075 -16.142 -0.067

H3PO4 3.798e-017 3.798e-017 -16.420 -16.420 0.000

H2P2O7-2 1.501e-017 8.037e-018 -16.824 -17.095 -0.271

FeHPO4 4.164e-020 4.164e-020 -19.380 -19.380 0.000

HPO3F- 2.068e-020 1.773e-020 -19.684 -19.751 -0.067

CaH2PO4+ 1.003e-020 8.597e-021 -19.999 -20.066 -0.067

MgH2PO4+ 5.718e-021 4.901e-021 -20.243 -20.310 -0.067

FeHPO4+ 1.771e-022 1.518e-022 -21.752 -21.819 -0.067

VO2HPO4- 1.686e-022 1.445e-022 -21.773 -21.840 -0.067

VO2(HPO4)2-3 1.462e-022 3.577e-023 -21.835 -22.447 -0.611

AlHPO4+ 1.631e-023 1.398e-023 -22.788 -22.855 -0.067

H3P2O7- 1.269e-026 1.088e-026 -25.897 -25.963 -0.067

H2PO3F 6.676e-031 6.676e-031 -30.175 -30.175 0.000

FeH2PO4+ 3.602e-032 3.087e-032 -31.443 -31.510 -0.067

H4P2O7 1.882e-036 1.882e-036 -35.725 -35.725 0.000

VO2H2PO4 6.024e-038 6.024e-038 -37.220 -37.220 0.000

AlH2PO4+2 7.599e-039 4.125e-039 -38.119 -38.385 -0.265

FeH2PO4+2 1.609e-039 8.735e-040 -38.793 -39.059 -0.265

S(6) 1.620e-003

SO4-2 1.497e-003 8.018e-004 -2.825 -3.096 -0.271

NaSO4- 1.231e-004 1.055e-004 -3.910 -3.977 -0.067

CaSO4 1.620e-008 1.620e-008 -7.791 -7.791 0.000

MgSO4 9.275e-009 9.275e-009 -8.033 -8.033 0.000

HSO4- 5.565e-013 4.769e-013 -12.255 -12.322 -0.067

FeSO4 3.162e-021 3.162e-021 -20.500 -20.500 0.000

VO2SO4- 1.808e-026 1.550e-026 -25.743 -25.810 -0.067

H2SO4 2.650e-027 2.650e-027 -26.577 -26.577 0.000

AlSO4+ 1.267e-027 1.086e-027 -26.897 -26.964 -0.067

Al(SO4)2- 7.888e-029 6.760e-029 -28.103 -28.170 -0.067

FeSO4+ 2.159e-030 1.851e-030 -29.666 -29.733 -0.067

Fe(SO4)2- 2.927e-032 2.509e-032 -31.534 -31.601 -0.067

VOSO4 3.510e-035 3.510e-035 -34.455 -34.455 0.000

VSO4+ 0.000e+000 0.000e+000 -54.201 -54.268 -0.067

Se(-2) 0.000e+000

HSe- 0.000e+000 0.000e+000 -57.377 -57.444 -0.067

Se-2 0.000e+000 0.000e+000 -60.889 -61.160 -0.271

H2Se 0.000e+000 0.000e+000 -64.852 -64.852 0.000

Se(4) 1.791e-007

SeO3-2 1.791e-007 9.593e-008 -6.747 -7.018 -0.271

HSeO3- 1.355e-011 1.161e-011 -10.868 -10.935 -0.067

H2SeO3 2.597e-020 2.597e-020 -19.586 -19.586 0.000

Se(6) 4.970e-006

SeO4-2 4.970e-006 2.662e-006 -5.304 -5.575 -0.271

HSeO4- 1.556e-015 1.333e-015 -14.808 -14.875 -0.067

Si 2.674e-003

176

HSiO3- 1.426e-003 1.222e-003 -2.846 -2.913 -0.067

NaHSiO3 1.147e-003 1.147e-003 -2.940 -2.940 0.000

SiO2 6.305e-005 6.305e-005 -4.200 -4.200 0.000

H2SiO4-2 3.717e-005 1.991e-005 -4.430 -4.701 -0.271

H4(H2SiO4)4-4 1.835e-007 1.500e-008 -6.736 -7.824 -1.088

H6(H2SiO4)4-2 1.937e-008 1.037e-008 -7.713 -7.984 -0.271

SiF6-2 0.000e+000 0.000e+000 -53.747 -54.018 -0.271

V(3) 1.272e-038

V(OH)2+ 1.272e-038 1.090e-038 -37.895 -37.962 -0.067

VOH+2 0.000e+000 0.000e+000 -45.267 -45.533 -0.265

V+3 0.000e+000 0.000e+000 -53.917 -54.502 -0.586

VSO4+ 0.000e+000 0.000e+000 -54.201 -54.268 -0.067

V2(OH)2+4 0.000e+000 0.000e+000 -89.325 -90.346 -1.021

V(4) 6.135e-029

VOOH+ 6.135e-029 5.258e-029 -28.212 -28.279 -0.067

VO+2 2.670e-034 1.449e-034 -33.574 -33.839 -0.265

VOSO4 3.510e-035 3.510e-035 -34.455 -34.455 0.000

VOF+ 1.033e-035 8.851e-036 -34.986 -35.053 -0.067

VOF2 3.257e-038 3.257e-038 -37.487 -37.487 0.000

(VO)2(OH)2+2 0.000e+000 0.000e+000 -51.623 -51.888 -0.265

V(5) 3.321e-005

VO3OH-2 3.014e-005 1.615e-005 -4.521 -4.792 -0.271

HVO4-2 3.001e-006 1.607e-006 -5.523 -5.794 -0.271

VO4-3 6.158e-008 1.507e-008 -7.211 -7.822 -0.611

H2VO4- 1.340e-009 1.149e-009 -8.873 -8.940 -0.067

VO2(OH)2- 8.561e-010 7.337e-010 -9.067 -9.134 -0.067

VO(OH)3 4.321e-017 4.321e-017 -16.364 -16.364 0.000

VO2HPO4- 1.686e-022 1.445e-022 -21.773 -21.840 -0.067

VO2(HPO4)2-3 1.462e-022 3.577e-023 -21.835 -22.447 -0.611

VO2+ 5.932e-025 5.084e-025 -24.227 -24.294 -0.067

VO2SO4- 1.808e-026 1.550e-026 -25.743 -25.810 -0.067

VO2F 6.951e-027 6.951e-027 -26.158 -26.158 0.000

VO2F2- 1.428e-029 1.224e-029 -28.845 -28.912 -0.067

VO2H2PO4 6.024e-038 6.024e-038 -37.220 -37.220 0.000

------------------------------Saturation indices-------------------------------

Phase SI log IAP log KT

(VO)3(PO4)2 -134.60 -85.81 48.79 (VO)3(PO4)2

Afwillite -21.56 38.40 59.96 Ca3Si2O4(OH)6

Akermanite -7.33 37.90 45.23 Ca2MgSi2O7

Al -124.30 25.62 149.91 Al

Al(g) -175.00 25.62 200.62 Al

Al2(SO4)3 -81.94 -63.04 18.90 Al2(SO4)3

Al2(SO4)3:6H2O -64.60 -63.05 1.56 Al2(SO4)3:6H2O

Albite 1.08 3.74 2.66 NaAlSi3O8

Albite_high -0.24 3.74 3.98 NaAlSi3O8

Albite_low 1.08 3.74 2.66 NaAlSi3O8

AlF3 -25.26 -42.52 -17.27 AlF3

Amesite-14A 3.95 79.23 75.27 Mg4Al4Si2O10(OH)8

Analcime 1.06 7.12 6.06 Na.96Al.96Si2.04O6:H2O

Analcime-dehy -5.30 7.12 12.42 Na.96Al.96Si2.04O6

Andalusite -6.46 9.42 15.88 Al2SiO5

Andradite 11.15 44.33 33.19 Ca3Fe2(SiO4)3

Anhydrite -5.61 -9.96 -4.35 CaSO4

Anorthite -5.65 20.82 26.48 CaAl2(SiO4)2

Antarcticite -14.78 -10.69 4.09 CaCl2:6H2O

Anthophyllite 5.59 72.07 66.48 Mg7Si8O22(OH)2

Antigorite 106.17 581.80 475.63 Mg48Si34O85(OH)62

Arsenolite -118.94 -138.78 -19.84 As2O3

As -93.27 -50.58 42.68 As

As2O5 -104.93 -102.79 2.14 As2O5

As4O6(cubi) -237.73 -277.56 -39.82 As4O6

As4O6(mono) -237.51 -277.56 -40.05 As4O6

B -96.58 12.98 109.56 B

B(g) -187.86 12.98 200.84 B

B2O3 -17.20 -11.65 5.55 B2O3

Bassanite -6.25 -9.96 -3.71 CaSO4:0.5H2O

Beidellite-Ca -2.41 3.03 5.44 Ca.165Al2.33Si3.67O10(OH)2

Beidellite-H -4.03 0.45 4.49 H.33Al2.33Si3.67O10(OH)2

177

Beidellite-Mg -2.46 2.95 5.41 Mg.165Al2.33Si3.67O10(OH)2

Beidellite-Na -1.90 3.60 5.50 Na.33Al2.33Si3.67O10(OH)2

Berlinite -11.76 -19.02 -7.27 AlPO4

BF3(g) -52.18 -55.16 -2.98 BF3

Bischofite -15.59 -11.19 4.39 MgCl2:6H2O

Bloedite -14.48 -16.96 -2.48 Na2Mg(SO4)2:4H2O

Boehmite -0.74 6.81 7.55 AlO2H

Borax -16.29 -4.25 12.04 Na2(B4O5(OH)4):8H2O

Boric_acid -5.67 -5.83 -0.16 B(OH)3

Brucite -1.19 15.10 16.28 Mg(OH)2

Brushite -16.79 -10.24 6.55 CaHPO4:2H2O

Ca -111.69 28.14 139.83 Ca

Ca(g) -136.93 28.14 165.07 Ca

Ca-Al_Pyroxene -10.88 25.02 35.90 CaAl2SiO6

Ca2Al2O5:8H2O -14.75 44.82 59.57 Ca2Al2O5:8H2O

Ca2Cl2(OH)2:H2O -21.38 4.91 26.29 Ca2Cl2(OH)2:H2O

Ca2V2O7 -12.11 -51.82 -39.71 Ca2V2O7

Ca3(AsO4)2 -73.79 -55.99 17.80 Ca3(AsO4)2

Ca3(AsO4)2:10H2O -71.52 -92.73 -21.21 Ca3(AsO4)2:10H2O

Ca3(AsO4)2:3H2O -71.59 -92.73 -21.14 Ca3(AsO4)2:3H2O

Ca3Al2O6 -52.61 60.42 113.03 Ca3Al2O6

Ca3V2O8 -17.90 -36.22 -18.32 Ca3V2O8

Ca4Al2Fe2O10 -54.32 86.16 140.48 Ca4Al2Fe2O10

Ca4Al2O7:13H2O -31.23 76.02 107.25 Ca4Al2O7:13H2O

Ca4Al2O7:19H2O -27.66 76.02 103.68 Ca4Al2O7:19H2O

Ca4Cl2(OH)6:13H2O -32.22 36.11 68.33 Ca4Cl2(OH)6:13H2O

Ca5(AsO4)3(OH) -105.19 -145.31 -40.12 Ca5(AsO4)3(OH)

CaAl2O4 -17.69 29.22 46.91 CaAl2O4

CaAl2O4:10H2O -8.77 29.22 37.99 CaAl2O4:10H2O

CaAl4O7 -25.75 42.85 68.59 CaAl4O7

CaCrO4 -10.65 -13.80 -3.15 CaCrO4

CaHAsO4 -39.91 -42.57 -2.66 CaHAsO4

CaHAsO4:H2O -37.78 -42.57 -4.79 CaHAsO4:H2O

CaSeO3:2H2O -9.24 -13.88 -4.63 CaSeO3:2H2O

CaSeO3:H2O -7.04 -13.88 -6.84 CaSeO3:H2O

CaSeO4 -9.34 -12.43 -3.09 CaSeO4

CaSeO4:2H2O -9.75 -12.43 -2.68 CaSeO4:2H2O

CaSO4:0.5H2O(beta) -6.42 -9.96 -3.54 CaSO4:0.5H2O

CaV2O6 -16.06 -67.42 -51.36 CaV2O6

Chalcedony -0.44 -4.20 -3.76 SiO2

Chamosite-7A -17.62 15.13 32.76 Fe2Al2SiO5(OH)4

Chloromagnesite -33.01 -11.19 21.82 MgCl2

Chromite -16.63 -1.47 15.16 FeCr2O4

Chrysotile 5.86 36.89 31.03 Mg3Si2O5(OH)4

Cl2(g) -41.82 -38.83 2.99 Cl2

Claudetite -118.98 -138.78 -19.80 As2O3

Clinochlore-14A 9.45 76.50 67.05 Mg5Al2Si3O10(OH)8

Clinochlore-7A 6.08 76.50 70.42 Mg5Al2Si3O10(OH)8

Clinoptilolite-Ca -2.90 -10.42 -7.52

Ca1.7335Al3.45Fe.017Si14.533O36:10.922H2O

Clinoptilolite-dehy-Ca -38.56 -10.42 28.14 Ca1.7335Al3.45Fe.017Si14.533O36

Clinoptilolite-dehy-Na -32.43 -4.42 28.01 Na3.467Al3.45Fe.017Si14.533O36

Clinoptilolite-hy-Ca -2.90 -10.42 -7.52

Ca1.7335Al3.45Fe.017Si14.533O36:11.645H2O

Clinoptilolite-hy-Na 3.22 -4.42 -7.65

Na3.467Al3.45Fe.017Si14.533O36:10.877H2O

Clinoptilolite-Na 3.22 -4.42 -7.64 Na3.467Al3.45Fe.017Si14.533O36:10.922H2O

Clinozoisite -4.07 39.03 43.10 Ca2Al3Si3O12(OH)

Coesite -0.98 -4.20 -3.22 SiO2

Colemanite -25.27 -3.76 21.51 Ca2B6O11:5H2O

Cordierite_anhyd -15.63 36.44 52.07 Mg2Al4Si5O18

Cordierite_hydr -13.15 36.44 49.59 Mg2Al4Si5O18:H2O

Corundum -4.67 13.62 18.29 Al2O3

Cr -82.03 16.64 98.67 Cr

Cr-ettringite -41.27 19.01 60.28 Ca6(Al(OH)6)2(CrO4)3:26H2O

Cr-monosulfoaluminate -24.74 46.62 71.36 Ca4Al2(OH)12(CrO4):9H2O

CrCl3 -59.52 -41.60 17.92 CrCl3

CrF3 -42.86 -51.50 -8.64 CrF3

CrF4 -81.10 -93.43 -12.34 CrF4

Cristobalite(alpha) -0.72 -4.20 -3.48 SiO2

Cristobalite(beta) -1.17 -4.20 -3.03 SiO2

178

CrO2 -8.52 -27.66 -19.14 CrO2

CrO3 -25.84 -29.40 -3.56 CrO3

Cronstedtite-7A -4.53 11.64 16.18 Fe2Fe2SiO5(OH)4

Daphnite-14A -36.80 15.30 52.10 Fe5AlAlSi3O10(OH)8

Daphnite-7A -40.18 15.30 55.48 Fe5AlAlSi3O10(OH)8

Diaspore -0.34 6.81 7.15 AlHO2

Dicalcium_silicate -10.13 27.00 37.13 Ca2SiO4

Diopside 1.41 22.30 20.89 CaMgSi2O6

Downeyite -22.69 -29.48 -6.79 SeO2

Enstatite -0.39 10.90 11.29 MgSiO3

Epidote 4.52 37.29 32.77 Ca2FeAl2Si3O12OH

Epidote-ord 4.52 37.29 32.76 FeCa2Al2(OH)(SiO4)3

Epsomite -8.50 -10.46 -1.96 MgSO4:7H2O

Eskolaite -11.97 -21.19 -9.22 Cr2O3

Ettringite -31.92 30.55 62.46 Ca6Al2(SO4)3(OH)12:26H2O

F2(g) -101.14 -45.43 55.71 F2

Fayalite -17.55 1.51 19.06 Fe2SiO4

Fe -43.62 15.39 59.02 Fe

Fe(OH)2 -11.04 2.86 13.89 Fe(OH)2

Fe(OH)3 -0.57 5.07 5.64 Fe(OH)3

Fe2(SO4)3 -69.58 -66.53 3.05 Fe2(SO4)3

FeF2 -27.61 -30.03 -2.42 FeF2

FeF3 -25.01 -44.26 -19.26 FeF3

FeO -10.67 2.86 13.52 FeO

Ferrite-Ca 4.24 25.73 21.50 CaFe2O4

Ferrite-Dicalcium -15.46 41.33 56.80 Ca2Fe2O5

Ferrite-Mg 4.21 25.23 21.02 MgFe2O4

Ferroselite -87.62 -168.44 -80.82 FeSe2

Ferrosilite -8.75 -1.34 7.41 FeSiO3

FeSO4 -25.31 -22.70 2.61 FeSO4

FeV2O4 -319.33 -38.77 280.56 FeV2O4

Fix_H+ -11.23 -11.23 0.00 H+

Fluorapatite 9.21 -15.95 -25.16 Ca5(PO4)3F

Fluorite -7.22 -17.29 -10.07 CaF2

Forsterite -1.82 25.99 27.81 Mg2SiO4

Foshagite -16.00 49.80 65.80 Ca4Si3O9(OH)2:0.5H2O

Gehlenite -15.60 40.62 56.22 Ca2Al2SiO7

Gibbsite -0.93 6.81 7.74 Al(OH)3

Gismondine -0.08 41.64 41.72 Ca2Al4Si4O16:9H2O

Glauberite -10.98 -16.45 -5.47 Na2Ca(SO4)2

Goethite 4.54 5.07 0.53 FeOOH

Greenalite -22.42 0.17 22.58 Fe3Si2O5(OH)4

Grossular -3.95 47.82 51.78 Ca3Al2(SiO4)3

Gypsum -5.42 -9.96 -4.53 CaSO4:2H2O

Gyrolite -4.20 18.60 22.80 Ca2Si3O7(OH)2:1.5H2O

H2(g) -30.46 -33.56 -3.10 H2

H2O(g) -1.59 -0.00 1.59 H2O

Halite -5.18 -3.61 1.56 NaCl

Hatrurite -30.75 42.60 73.35 Ca3SiO5

HCl(g) -19.45 -13.14 6.30 HCl

Hedenbergite -9.47 10.06 19.53 CaFe(SiO3)2

Hematite 10.06 10.13 0.08 Fe2O3

Hercynite -12.32 16.48 28.80 FeAl2O4

Hexahydrite -8.73 -10.46 -1.73 MgSO4:6H2O

Hillebrandite -9.77 27.00 36.77 Ca2SiO3(OH)2:0.17H2O

Hydroboracite -24.63 -4.26 20.36 MgCaB6O11:6H2O

Hydrophilite -22.43 -10.69 11.75 CaCl2

Hydroxylapatite 3.72 0.49 -3.22 Ca5(OH)(PO4)3

Ice -0.14 -0.00 0.14 H2O

Jadeite -0.37 7.94 8.31 NaAl(SiO3)2

Jarosite-Na -20.93 -26.38 -5.45 NaFe3(SO4)2(OH)6

Kaolinite -1.50 5.22 6.72 Al2Si2O5(OH)4

Karelianite -51.57 -41.63 9.95 V2O3

Katoite -18.52 60.42 78.94 Ca3Al2H12O12

Kieserite -10.19 -10.46 -0.27 MgSO4:H2O

Kyanite -6.19 9.42 15.61 Al2SiO5

Larnite -11.42 27.00 38.42 Ca2SiO4

Laumontite -1.09 12.42 13.51 CaAl2Si4O12:4H2O

Lawrencite -32.49 -23.43 9.05 FeCl2

Lawsonite -1.28 20.82 22.11 CaAl2Si2O7(OH)2:H2O

Lime -16.97 15.60 32.57 CaO

179

Magnesiochromite -10.92 10.77 21.69 MgCr2O4

Magnetite 2.57 12.99 10.42 Fe3O4

Margarite -6.48 34.44 40.93 CaAl4Si2O10(OH)2

Mayenite -211.59 282.56 494.15 Ca12Al14O33

Melanterite -20.30 -22.70 -2.40 FeSO4:7H2O

Merwinite -14.91 53.50 68.41 MgCa3(SiO4)2

Mesolite 4.11 17.60 13.49 Na.676Ca.657Al1.99Si3.01O10:2.647H2O

Mg -94.89 27.63 122.52 Mg

Mg(g) -114.61 27.63 142.25 Mg

Mg1.25SO4(OH)0.5:0.5H2O -11.88 -6.69 5.20 Mg1.25SO4(OH)0.5:0.5H2O

Mg1.5SO4(OH) -12.12 -2.91 9.21 Mg1.5SO4(OH)

Mg2V2O7 -21.93 -52.83 -30.90 Mg2V2O7

MgCl2:2H2O -23.92 -11.19 12.73 MgCl2:2H2O

MgCl2:4H2O -18.49 -11.19 7.30 MgCl2:4H2O

MgCl2:H2O -27.26 -11.19 16.07 MgCl2:H2O

MgOHCl -13.94 1.95 15.89 MgOHCl

MgSeO3 -16.05 -14.38 1.67 MgSeO3

MgSeO3:6H2O -10.95 -14.38 -3.44 MgSeO3:6H2O

MgSO4 -15.29 -10.46 4.83 MgSO4

MgV2O6 -22.08 -67.93 -45.85 MgV2O6

Minnesotaite -22.07 -8.24 13.83 Fe3Si4O10(OH)2

Mirabilite -5.35 -6.50 -1.15 Na2SO4:10H2O

Mo -99.94 9.33 109.27 Mo

Molysite -47.83 -34.36 13.47 FeCl3

Monosulfoaluminate -22.11 50.46 72.57 Ca4Al2(SO4)(OH)12:13H2O

Monticellite -3.03 26.50 29.53 CaMgSiO4

Montmor-Ca -0.22 2.13 2.34 Ca.165Mg.33Al1.67Si4O10(OH)2

Montmor-Mg -0.19 2.05 2.23 Mg.495Al1.67Si4O10(OH)2

Montmor-Na 0.37 2.70 2.33 Na.33Mg.33Al1.67Si4O10(OH)2

Mordenite -1.53 -6.90 -5.36 Ca.2895Na.361Al.94Si5.06O12:3.468H2O

Mordenite-dehy -16.66 -6.89 9.77 Ca.2895Na.361Al.94Si5.06O12

MoSe2 -127.86 -182.98 -55.12 MoSe2

Na -51.57 15.80 67.37 Na

Na(g) -65.06 15.80 80.86 Na

Na2Cr2O7 -29.56 -39.74 -10.18 Na2Cr2O7

Na2CrO4 -13.24 -10.34 2.90 Na2CrO4

Na2O -48.36 19.06 67.42 Na2O

Na2Se -76.39 -64.56 11.83 Na2Se

Na2Se2 -99.36 -160.72 -61.35 Na2Se2

Na2SiO3 -7.34 14.86 22.20 Na2SiO3

Na3H(SO4)2 -21.63 -22.52 -0.89 Na3H(SO4)2

Na4Ca(SO4)3:2H2O -17.06 -22.95 -5.89 Na4Ca(SO4)3:2H2O

Na4SiO4 -36.68 33.92 70.60 Na4SiO4

Na6Si2O7 -52.76 48.77 101.53 Na6Si2O7

NaFeO2 -5.29 14.60 19.88 NaFeO2

Natrolite 1.69 20.08 18.39 Na2Al2Si3O10:2H2O

Natrosilite -7.41 10.66 18.07 Na2Si2O5

Nepheline -1.61 12.14 13.75 NaAlSiO4

NO2(g) -18.23 -9.89 8.35 NO2

Nontronite-Ca 11.27 -0.46 -11.73 Ca.165Fe2Al.33Si3.67H2O12

Nontronite-H 9.66 -3.03 -12.69 H.33Fe2Al.33Si3.67H2O12

Nontronite-Mg 11.23 -0.54 -11.77 Mg.165Fe2Al.33Si3.67H2O12

Nontronite-Na 11.79 0.11 -11.68 Na.33Fe2Al.33Si3.67H2O12

O2(g) -22.18 -25.08 -2.89 O2

Okenite -3.11 7.20 10.31 CaSi2O4(OH)2:H2O

Oxychloride-Mg -8.78 17.05 25.83 Mg2Cl(OH)3:4H2O

P -126.54 5.51 132.05 P

Paragonite -0.02 17.36 17.38 NaAl3Si3O10(OH)2

Pargasite -5.35 96.35 101.70 NaCa2Al3Mg4Si6O22(OH)2

Pentahydrite -9.07 -10.46 -1.39 MgSO4:5H2O

Periclase -6.23 15.10 21.33 MgO

Portlandite -6.95 15.60 22.55 Ca(OH)2

Prehnite -0.57 32.22 32.79 Ca2Al2Si3O10(OH)2

Pseudowollastonite -2.56 11.40 13.96 CaSiO3

Pyrophyllite -3.47 -3.18 0.29 Al2Si4O10(OH)2

Quartz -0.17 -4.20 -4.03 SiO2

Rankinite -13.42 38.40 51.82 Ca3Si2O7

Ripidolite-14A -8.76 52.02 60.78 Mg3Fe2Al2Si3O10(OH)8

Ripidolite-7A -12.14 52.02 64.16 Mg3Fe2Al2Si3O10(OH)8

Saponite-Ca 8.55 34.70 26.14 Ca.165Mg3Al.33Si3.67O10(OH)2

Saponite-H 6.94 32.12 25.18 H.33Mg3Al.33Si3.67O10(OH)2

180

Saponite-Mg 8.51 34.61 26.10 Mg3.165Al.33Si3.67O10(OH)2

Saponite-Na 9.07 35.27 26.20 Na.33Mg3Al.33Si3.67O10(OH)2

Scolecite 0.88 16.62 15.75 CaAl2Si3O10:3H2O

Se -30.50 -4.40 26.10 Se

Se-ettringite -38.18 23.11 61.29 Ca6(Al(OH)6)2(SeO4)3:31.5H2O

Se-monosulfoaluminate -25.42 47.98 73.40 Ca4(Al(OH)6)2SeO4:9H2O

Se2O5 -67.00 -57.51 9.49 Se2O5

SeCl4 -96.39 -82.05 14.33 SeCl4

Sellaite -8.35 -17.79 -9.44 MgF2

SeO3 -47.20 -28.03 19.16 SeO3

Sepiolite 4.96 35.18 30.22 Mg4Si6O15(OH)2:6H2O

Shcherbinaite -24.68 -26.13 -1.45 V2O5

Si -127.99 20.88 148.86 Si

Si(g) -199.06 20.88 219.94 Si

SiF4(g) -54.74 -69.98 -15.24 SiF4

Sillimanite -6.82 9.42 16.24 Al2SiO5

SiO2(am) -1.46 -4.20 -2.74 SiO2

Spinel -8.89 28.72 37.61 Al2MgO4

Starkeyite -9.46 -10.46 -1.00 MgSO4:4H2O

Strengite -9.38 -20.77 -11.39 FePO4:2H2O

Tachyhydrite -50.22 -33.07 17.14 Mg2CaCl6:12H2O

Talc 7.50 28.49 20.99 Mg3Si4O10(OH)2

Thenardite -6.14 -6.50 -0.36 Na2SO4

Tobermorite-11A -12.59 52.80 65.39 Ca5Si6H11O22.5

Tobermorite-14A -10.81 52.80 63.61 Ca5Si6H21O27.5

Tobermorite-9A -16.06 52.80 68.86 Ca5Si6H6O20

Tremolite 12.15 73.08 60.93 Ca2Mg5Si8O22(OH)2

Tridymite -0.36 -4.20 -3.84 SiO2

V -108.95 -2.01 106.94 V

V2O4 -31.32 -22.76 8.56 V2O4

V3O5 -66.43 -53.01 13.43 V3O5

V4O7 -83.18 -64.38 18.80 V4O7

Vivianite -38.38 -43.11 -4.72 Fe3(PO4)2:8H2O

Wairakite -5.50 12.42 17.92 CaAl2Si4O10(OH)4

Whitlockite -0.55 -4.87 -4.32 Ca3(PO4)2

Wollastonite -2.32 11.40 13.72 CaSiO3

Wustite -9.46 2.94 12.40 Fe.947O

Xonotlite -23.34 68.40 91.74 Ca6Si6O17(OH)2

Zoisite -4.10 39.03 43.14 Ca2Al3(SiO4)3OH

------------------

End of simulation.

------------------

181

APPENDIX H: MOLAL CONCENTRATION OF ELEMENTS OBTAINED FROM

THE MODEL

TABLE H-1: Molal concentration from simulation at pH 11.588

GPC GP1 GP2 GP3

As(5)

mol/l 1.371E-05 1.365E-05 1.360E-05 1.239E-05

mg/l 1.027 1.023 1.019 0.928

Cr(3)

mol/l 3.863E-28 5.440E-28 3.776E-28 4.268E-28

mg/l 2.008E-23 2.828E-23 1.963E-23 2.219E-23

Cr(5)

mol/l 5.570E-12 6.254E-12 5.566E-12 5.479E-12

mg/l 2.896E-07 3.251E-07 2.894E-07 2.849E-07

Cr(6)

mol/l 2.164E-07 2.164E-07 2.164E-07 2.164E-07

mg/l 0.011 0.011 0.011 0.011

Se(4)

mol/l 2.386E-13 3.096E-13 2.455E-13 2.313E-13

mg/l 1.884E-08 2.445E-08 1.938E-08 1.826E-08

Se(6)

mol/l 5.149E-06 5.315E-06 5.366E-06 4.749E-06

mg/l 0.407 0.420 0.424 0.375

Documents

BASED GEOPOLYMER CONCRETE A dissertation …libres.uncg.edu/ir/uncc/f/Sanusi_uncc_0694D_10405.pdf · 8.1.2 Description of the PHREEPLOT Input File 119 8.2 Procedure for the PHREEPLOT